System and method for automatically reconnecting a wireless interface device to a host computer

ABSTRACT

A wireless interface device is adapted to be connected to a host computer. On power-up, a list of available hosts is identified in a dialog box on the display of the wireless interface device. Once a host is selected, the node address for the selected host is stored in an EEPROM. On a subsequent power-up of the wireless interface device, a connection is automatically made to the last selected host.

CROSS-REFERENCE TO RELATED CASES

This case is a continuation-in-part of to the following copendingapplication: STRUCTURE AND METHOD FOR CONTROLLING A HOST COMPUTER USINGA REMOTE HAND-HELD INTERFACE DEVICE, by B. R. Banerjee, S. C. Gladwin,A. Maskatia and A. Soucy, filed Sep. 2, 1994, Ser. No. 08/300,500. Thiscase is also related to the following copending applications, all filedon even date: REMOTE CONTROL INTERFACE, by B. R. Banerjee, S. C.Gladwin, A. Maskatia and A. Soucy Ser. No. 08/543,700; RADIO FLASHUPDATE, by D. Bi, H. Hsiung and J. Wilson, Ser. No. 08/543,463; MOUSEEMULATION WITH PASSIVE PEN, by D. Bi, G. Cohen, M. Cortopassi, J.George, S. C. Gladwin, H. Hsiung, P. Lim, J. Parham, A. Soucy, D.Voegeli and J. Wilson, Ser. No. 08/543,786, now abandoned in favor ofcontinuation U.S. patent application Ser. No. 08/957,398, filed on Oct.23, 1997; RESUME ON PEN CONTACT, by M. Cortopassi, S. C. Gladwin and D.Voegeli, Ser. No. 08/543,510; SCREEN SAVER DISABLER, by D. Bi, S. C.Gladwin and J. Wilson, Ser. No. 08/543,698; IPX DRIVER FOR MULTIPLE LANADAPTERS, by D. Bi, Ser. No. 08/553,808; DISASTER RECOVERY JUMPER, by M.Cortopassi, J. George, J. Parham and D. Voegeli, Ser. No. 08/543,423; RCTIME CONSTANT, by M. Cortopassi, Ser. No. 08/543,697; DOUBLE PEN UPEVENT, by D. Bi and J. George, Ser. No. 08/543,787; REMOTE OCCLUSIONREGION, by J. Wilson, Ser. No. 08/543,701; BROADCAST SEARCH FORAVAILABLE HOST, by D. Bi, S. C. Gladwin and J. Wilson, Ser. No.08/543,599; REMOTE KEYBOARD MACROS ACTIVATED BY HOT ICONS, by S. C.Gladwin and J. Wilson, Ser. No. 08/543,788; HOST/REMOTE CONTROL MODE, byM. Cortopassi, J. George, S. C. Gladwin, H. Hsiung, P. Lim, J. Parham,D. Voegeli and J. Wilson, Ser. No. 08/551,936; PASSWORD SWITCH TOOVERRIDE REMOTE CONTROL, by D. Bi, S. C. Gladwin and J. Wilson, Ser. No.08/543,785; and PORTABLE TABLET, by G. Cohen, S. C. Gladwin, P. Lim, J.Smith, A. Soucy, K. Swen, G. Wong, Ken K. Wood and G. Wu, Ser. No.29/045,319, now U.S. Design Pat. No. 385,857 issued on Nov. 14, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless interface device and moreparticularly to a wireless interface for interfacing with a hostcomputer. On power-up, the wireless interface device ascertains theavailable hosts for connection. Once a host is selected, the nodeaddress for that host is stored in an EEPROM, such that on subsequentpower-ups the wireless interface device will automatically be connectedto the last host selected.

2. Description of the Prior Art

Both wired and wireless LAN systems are known in the art. Such systemsenable various desktop and/or portable personal computers to beconnected in a local area network in order to share resources. WirelessLAN systems are normally used in an office environment to enable thevarious users to share common resources while obviating the need fordirect wire connections between the personal computers connected to theLAN.

The personal computers connected to a wireless LAN configuration arenormally equipped with a wireless LAN card and a radio interface whichtypically includes a spread-spectrum type radio to reduce interference.

As mentioned above, portable personal computers have been known to beused in such wireless LAN systems. However, portable personal computers,even such notebook-size portable personal computers, are cumbersome totransport in an office environment. Unfortunately, the resources of theLAN system are often needed at locations other than where the personalcomputers connected to the LAN are located.

In both wired and wireless LAN systems, the node addresses of thepersonal computers to be connected to the LAN must be known before anycommunication is established. Thus, interfacing abilities of suchsystems are rather limited.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve various problems ofthe prior art.

It is yet another object of the present invention to provide a wirelessinterface device that is adapted to be connected to one of a pluralityof available hosts and automatically reconnected to the last selectedhost on power-up.

Briefly, the present invention relates to a wireless interface devicefor connection to a host computer. On power-up, a list of availablehosts is identified in a dialog box on the display of the wirelessinterface device. Once a host is selected, the node address for theselected host is stored in an EEPROM. On a subsequent power-up of thewireless interface device, connection is automatically made to the lastselected host.

BRIEF DESCRIPTION OF THE DRAWING

These and other objects of the present invention will be readilyunderstood upon consideration of the following detailed description andattached drawing, wherein:

FIG. 1 is a block diagram of the hardware configuration of a wirelessinterface device in accordance with the present invention and a hostcomputer;

FIG. 2 is a block diagram illustrating the access of the wirelessinterface device in accordance with the present invention and a wiredlocal area network;

FIG. 3 is a diagram illustrating the software structure for the wirelessinterface device in accordance with the present invention;

FIG. 4 is a block diagram showing one implementation of the wirelessinterface device of FIG. 1;

FIG. 5 is a state diagram illustrating the six internal power managementstates of the wireless interface device;

FIG. 6 is a block diagram illustrating the operational states of thewireless interface device under the control of dedicated Viewer Managersoftware in accordance with the present invention;

FIG. 7 is a block diagram of the software environment under which thewireless interface device and the host computer operate to provideremote control of the host computer;

FIG. 8 is a block diagram which shows in further detail the softwareenvironment in the host computer, running an application program under aWindows environment;

FIG. 9 is a block diagram which shows in further detail the softwareenvironment in the wireless interface device, running in a normaloperation state;

FIG. 10 is a block diagram illustrating the method used in the wirelessinterface device to anticipate a pen/mouse mode decision;

FIGS. 11-30 are schematic diagrams of the wireless interface device inaccordance with the present invention;

FIGS. 31-35 are flow charts relating to mouse emulation with a passivepen;

FIG. 36 is a plan view of the wireless interface device illustrating thehot icon area and viewing area of the display;

FIG. 37 illustrates the hot icons in the hot icon area of the display;

FIGS. 38, 39 and 40 are flow charts relating to a system for disablingthe screen saver to reduce LAN traffic;

FIG. 40A is a flow chart relating to a host access protection passwordsystem;

FIGS. 41-43 are flow charts relating to a system for handling pen-upevents;

FIG. 44 is a configuration diagram illustrating the wireless interfacedevice interfacing with a wired LAN system;

FIG. 45 is a diagram of the software structure of a known networksystem;

FIG. 46 is a diagram of the software structure of network system whichenables the wireless interface device to interface with the wired LANsystem, illustrated in FIG. 44;

FIGS. 47-52 are flow charts relating to the seamless integration ofwired and wireless LANS;

FIGS. 53-57 are illustrations of various set-up dialog boxes availableon the wireless interface device;

FIG. 58 is a flow chart relating to the host control mode;

FIG. 59 is a flow chart relating to a system for broadcasting foravailable hosts;

FIGS. 60 and 61 are flow charts relating to a system for providingremote keyboard macros on the wireless interface device;

FIGS. 62 and 63 are flow charts relating to a wireless flash ROMprogrammer;

FIGS. 64A and 64B are flow charts relating to a system for providingautomatic reconnection of the host;

FIGS. 65A and 65B are flow charts relating to providing a remoteocclusion region on the wireless interface device; and

FIGS. 66A-66D illustrate the various configurations of an on-screenkeyboard available on the wireless interface device.

DETAILED DESCRIPTION OF THE INVENTION 1. General

The present invention relates to a system which allows wireless accessand control of a remote host computer, which may be either a desktop,tower or portable computer to enable remote access of the various filesand programs on the host computer. The system not only allows access toremote host computers that are configured as stand-alone units but alsoprovides access to both wired and wireless local area networks (LAN).

The system includes a wireless interface device which includes agraphical user interface (GUI) which allows various types of input. Inparticular, input to the wireless interface device is primarily by wayof a passive stylus, which can be used in a pen mode or a mouse mode.

In a pen mode, a trail of ink tracking the path of the stylus (penparadigm) provides visual feedback to the user by way of a pendigitizer. In a mouse mode, however, a cursor may be generated whichfollows the "tip" of the pen, but the path of cursor motion is notinked.

A virtual keyboard is also provided as part of the GUI. Activation ofthe keys on the virtual keyboard is by way of the stylus or by fingerinput. In addition, the system also supports a full-size externalkeyboard.

FIG. 1 illustrates a block diagram of the system 10 in accordance withthe present invention. In particular, a wireless interface device 100,in accordance with the present invention, enables wireless access of aremote host computer 101, configured as either a stand-alone unit or asa part of a wired or wireless local area network (LAN). When the remotehost computer 101 is in a stand-alone configuration, as illustrated inFIG. 1, communication between the remote host computer 101 and thewireless interface device 100 is by way of a wireless communicationlink, provided by a communication subsystem 118 in which the remote hostcomputer 101 is provided with a transceiver 115 for radio communicationwith a transceiver 116 in the wireless interface device 100. Forexample, the desktop or remote host computer 101 can be provided with aPCMCIA interface which can be used with a wireless transceiver card tocommunicate with the transceiver 116 in the wireless interface device100.

Alternatively, an Industry Standard Architecture (ISA) card transceivercan be installed in the host computer 101 in a spare ISA expansion slot.In particular, the transceivers 115 and 116 may be implemented as 2.4GHz radio frequency (RF) transceiver modules with a Wireless MediaAccess Control function, available from Proxim Inc., Mountain View,Calif., configured with either an ISA or PCMCIA interface.

As mentioned above, the wireless interface device 100 can also be usedwith a wireless LAN in a peer-to-peer network or a wired LAN. FIG. 2illustrates the communication between the wireless interface device 100and a wired LAN 114, which includes a server 108 in a, for example,Novell Netware or Microsoft LAN Manager environment. In this mode, thetransceiver 116 in the wireless interface device 100 communicates withan access point 109 by way of a transceiver (not shown), whichinterfaces the wireless interface device 100 with a wired LAN 114 whichincludes a server 108. Alternatively, the wireless interface device 100can be used in a wireless network in a Windows for Workgroups orPersonal Netware environment, for example.

The configuration of the radio communication subsystem between thewireless interface device 100 and the remote host computer 101 or accesspoint 109 conforms to the Open System Interconnection (OSI) referencemodel for data communications and implements the lower two layers of theseven-layer OSI model. In particular, with reference to FIG. 3, thephysical layer 107 (WIRELESS PHY) may be a 2.4 GHz spread spectrumfrequency hopping radio which replaces the LAN cable normally connectedbetween workstations. The radio operates within the 2.4000-2.4835 GHzband, the unlicensed Industrial Scientific and Medial (ISM) band, and isdivided into eighty-two 1 MHz channels. In a spread-spectrum,frequency-hopping radio, data is broadcast on one particular channel fora predetermined time (i.e. 400 msec); and then the system hops toanother channel in a predetermined pattern to avoid interference.

The wireless media access control (WIRELESS MAC) 106 is used tointerface to higher level software 105 (i.e. NOS SHELL, NOVELL,MICROSOFT) through network drivers 104 (i.e. LINK LEVEL INTERFACE (ODI,NDIS)). The MAC conforms to the industry standard protocol is inaccordance with IEEE 802.11.

As shown in FIG. 1, the wireless interface device 100 includes a centralprocessing unit (CPU) 112, a local memory system 111, a pen-based inputsubsystem (STYLUS) 110, a display subsystem 113 and a transceiver 116.As will be discussed in more detail below, the wireless interface device100 includes a Viewer Manager software 200 (FIG. 6) which performs three(3) basic functions: (i) collecting and transmitting input positionalinformation from a stylus input subsystem 110 to the host computer 101,(ii) receiving from the host computer 101 a video image to be displayedon the display subsystem 113, and (iii) managing the communications linkbetween the wireless interface device 100 and the host computer 101.

The wireless interface device 100 is thus able to control and accessvarious programs such as Windows and Windows application programs andfiles residing at the host computer 101 and display the results in itsdisplay 113.

2. Description of the Block Diagram

FIG. 4 is a block diagram of the wireless interface device 100. As shownin FIG. 4, the wireless interface device 100 has both a processor or"local bus" 150 and an ISA bus 151. The local bus 150 operates at theclock rate of the CPU 112, while the ISA bus 151 operates at theindustry standard 8 MHz clock rate. The CPU 112 may be implemented by amicroprocessor, which allows suspension and resumption of operation byhalting and restarting the system clock to reduce battery consumption.Because power management in a portable device is important, the CPU 112should preferably support power management functions, such as SystemManagement Mode (SMM) and System Management Interrupt (SMI) techniquesknown in the industry. One example of a suitable microprocessor is theAMD386DXLV, available from Advanced Micro Devices, Inc., Sunnyvale,Calif., which operates at up to 25 MHz at a 3.0 V supply voltage.

The CPU 112 interfaces over local bus 150 with a system controller 129.The system controller 129 manages (i) system operation, including thelocal and ISA buses 150 and 151, (ii) memory, and (iii) power to thesystem. The system controller 129 may be, for example, a Model No.86C368 integrated circuit, available from PicoPower Technology, Inc.,San Jose, Calif.

The present implementation takes advantage of the several levels ofpower management supported by the system controller 129. Powermanagement in the present implementation is described in further detailbelow.

The system controller 129 provides a dynamic random access memory (DRAM)controller and a non-volatile random access memory (NVRAM) controller tocontrol the DRAM 111A and a non-volatile RAM, NVRAM 111B, which form aportion of the memory subsystem 111 (FIG. 1) in the wireless interfacedevice 100. As shown in FIG. 4, the DRAM 111A in the wireless interfacedevice 100 may be provided by four 16-bit by 256 K DRAM memory chips, toprovide a total of 2 megabytes of memory, while the NVRAM 111B, used tostore configuration data and passwords, for example, may be implementedusing E² PROM technology to provide permanent storage.

All devices on the ISA bus 151 are managed by an integrated peripheralcontroller (IPC) 128. The IPC 128 provides various functions includingdirect memory access (DMA) control, interrupt control, a timer, a realtime clock (RTC) controller, and a memory mapper for mapping peripheraldevices to the system memory space as illustrated in Table 4 below. TheIPC 128 may be implemented by a Model No. PT82C206 integrated circuit,also available from the aforementioned PicoPower Technology, Inc.

The stylus input subsystem 110 is implemented by a stylus, a pencontroller 110A and a digitizer panel 110B. The pen controller 110Acontrols the digitizer panel 110B and provides positional information ofpen or stylus contact. The pen controller 110A can be implemented, forexample by a Model No. MC68HC705J2 microcontroller, available fromMotorola, Inc. In this implementation, the digitizer panel 110B can be,for example, an analog-resistive touch screen, so that the stylus issensed by mechanical pressure. Using a digitizer panel which sensesmechanical pressure allows a "dumb" stylus, or even the human finger, tobe used as an input device. When using a dumb stylus, switching betweenmouse and pen modes is accomplished by selecting an icon as discussedbelow. Alternately, other styli, such as a "light pen" or an electronicstylus with various operating modes, can also be used. In someelectronic stylus', switching between pen and mouse modes can beachieved by pushing a "barrel button" (i.e. a switch located on thebarrel of the stylus).

As mentioned above, the wireless interface device 100 includes a displaysubsystem 113 which, in turn, includes a liquid crystal display (LCD)113C. The LCD 113C is controlled by a video controller 113A, andsupported by video memory 113B. The video controller 113A can beimplemented by a Model No. CL-GD6205 video controller, available fromCirrus Logic Corporation, Milpitas, Calif. The LCD 113C can be, forexample, a monochrome display, such as the Epson EG9015D-NZ (from EpsonCorporation), or an active matrix color display. The video memory 113Bmay be implemented as DRAMs, organized as 256 K by 16 bits.

The video controller 113A communicates with video memory 113B over aseparate 16-bit video bus 113D. In this implementation, the videocontroller 113A provides "backlighting" support through a backlightcontrol pin BACKLITEON that is de-asserted to conserve power undercertain power management conditions as discussed below

As discussed above, the communication subsystem 118 allows communicationwith a remote host computer 101 in either a stand-alone configuration orconnected to either a wired or wireless LAN. The communication system118 includes the transceiver 116, an antenna 116A, and an RF controller114A for interfacing with the local ISA bus 151.

The wireless interface device 100 also includes a keyboard controller125 which performs, in addition to controlling an optional keyboard byway of a connector, various other functions including battery monitoringand LCD status control. The keyboard controller 125 can be implementedby a Model No. M38802M2 integrated circuit from Mitsubishi Corporation,Tokyo, Japan. Battery power to the wireless interface device 100 may beprovided by an intelligent battery pack (IBP) 131, for example, asdescribed in U.S. patent application Ser. No. 07/975,879, filed on Nov.13, 1992, hereby incorporated by reference, connected to a system powersupply module 133 by way of a battery connector 132. The IBP 131maintains and provides information about the remaining useful batterylife of IBP 131, monitored by keyboard controller 125. Upon theoccurrence of a significant event relative to the IBP 130, e.g. batteryremaining life falling below a preset value, the keyboard controller 125generates an interrupt signal.

A serial port is provided and implemented by way of a universalasynchronous receiver transmitter (UART) 134, which can be accessedexternally via a serial port connector 135. As will be discussed in moredetail below, the serial port connector 135 allows for disaster recoveryfor the flash memory 117, which may be used to store the basicinput/output (BIOS) for the CPU 112.

3. Power Management

In order to conserve battery power, the wireless interface device 100incorporates power management. While a user of the wireless interfacedevice 100 would normally only be aware of four power management states:"off"; "active"; "suspend"; and "sleep" modes, internally six powermanagement states are implemented as shown in FIG. 5. More particularly,with reference to FIG. 5, before the wireless interface device 100 ispowered up, the wireless interface device 100 is in an "off" state;indicated by the reference numeral 160. In an "off" state 160, no poweris supplied to the system. A state 161 (the "active" state) is enteredwhen the power switch (FIG. 28) to the wireless interface device 100 isturned to the "on" position. In the active state 161, all components ofwireless interface device 100 are active. From active state 161, thewireless interface device 100 enters a "local standby" state 162. Thelocal standby state 162 is transparent to the user of the wirelessinterface device 100. From the user's point of view, in the localstandby state 162, the wireless interface device 100 is in active mode.In this state 162, specific inactive devices are each put into a staticstate after a predetermined time-out period of inactivity for thatdevice. In a static state, each device consumes minimal power. In thelocal standby state 162, devices that can be put into static statesinclude the CPU 112, the video controller 113A, the pen controller 11A,the UART 134, and the transceiver 116. Backlighting of the LCD videodisplay is also disabled in local standby state 162. If not, inputactivities are detected by the keyboard controller 125 or pen controller110A. After the later of their respective present time-out periods,these devices are placed in a static state. These devices emerge fromthe static state once an activity relevant to its operation is detected,e.g. a pen event is detected.

The user of the wireless interface device 100 can place the wirelessinterface device 100 in a "sleep" mode 163 by selecting an icon (FIG.37) labelled "sleep" from the GUI as will be discussed below.Alternatively, the "sleep" mode may be entered from the active state 161after a preset period of inactivity. In a "sleep" mode, corresponding toeither "sleep" state 163 or "active sleep" state 164, the displaysubsystem 113 is switched off; and most devices are placed in staticstates. When a keyboard or pen event is detected, the sleep state 163and active sleep state 164 are exited, and the wireless interface device100 enters the active state 161. From the sleep state 163, an activesleep state 164 is entered when a communication packet is received fromthe host computer 101. Although the display subsystem 113 is turned off,the received communication packet can result in an update to an imagestored in the video memory 113B. The CPU 112 handles the communicationpacket from the host computer 101 and activates the video controller113A to update such an image. The active sleep state 164 is transparentto the user of the wireless interface device 100, since the updatedimage is not displayed on the LCD screen 113C. When the communicationpacket is handled, the wireless interface 100 returns to a sleep state163. The device activities in wireless interface device 100 in "sleep"mode 163 are illustrated in Table 1 below.

                  TABLE 1                                                         ______________________________________                                                        CLOCKS             WAKEUP                                       DEVICE STATE DISABLED COMMENTS SOURCE                                       ______________________________________                                        Micro-  Static  Clock Stop                                                                              Static Mode                                                                            Clock Restarted                              processor Suspend Control by entered when and Controlled                        the system clock stopped by the system                                        controller  controller                                                      System Static Clock  Activity on                                              Controller Suspend Stopped/32  EXACT,                                           KHz Left  SWITCH, or                                                          on  RING pins                                                               Peripheral Static 32 KHz  Any Interrupts                                      Controller  Source                                                            Main Slow System Memory                                                       Memory Refresh controller Refreshed at                                          38 KHz 128 mS                                                               Video Static 14 MHz Controlled When system is                                   disconnected through use resumed                                               of system                                                                     controller                                                                    power                                                                         management                                                                    pins                                                                       Video Slow 32 KHz Memory Video Controller                                     Memory   Refreshed at                                                            128 mS                                                                      Refresh   automatically                                                          adjusts refresh                                                               rate depending on                                                             mode                                                                      LCD Module OFF NA Power to Controlled by                                         Module will Video controller                                                  never be power up                                                             applied in sequencing                                                         Sleep                                                                      LCD OFF NA Backlight will Controlled by                                       Backlight   never be on Video controller                                         in Sleep power up                                                              sequencing                                                                UART Static 1.84 MHz Part has no                                                 direct power                                                                  management                                                                 UART Off NA Part turned Access to serial                                      Trans.   off, until port                                                         access to                                                                     UART.                                                                         Inactivity                                                                    timer will                                                                    start, and                                                                    look for a                                                                    time-out of                                                                   two minutes                                                                   before                                                                        turning off                                                                   transceiver                                                                ROM Static NA After ROM is                                                       shadowed,                                                                     the CS and                                                                    OE line will                                                                  be driven                                                                     high to keep                                                                  these parts in                                                                a static mode                                                              NVRAM Static NA After                                                            NVRAM is                                                                      read, the CS                                                                  line will be                                                                  high which                                                                    forces part                                                                   into a static                                                                 mode                                                                       Pen Sleep Own 4.0 Sleeps after Pen Down wakes                                 Controller  MHz each point is up Pen                                             processed as controller. Pen                                                  long as the controller asserts                                                pen is not the                                                                pressing the PEN.sub.-- ACTIVITY                                              screen signal which will                                                       wake up the                                                                   entire system.                                                            Hook Active Own 32 Keeps the last NA                                            KHz display as                                                                 told by the                                                                   keyboard                                                                      controller                                                                 Clock Active All Clocks Clocks                                                Generator  Running needed in                                                     order to wake                                                                 system back                                                                   up                                                                         Radio Sleep Internal Radio Wakes up on                                           Handles its periodic basis in                                                 own power order to keep                                                       management SYNC. When a                                                        packet is ready,                                                              the Radio will                                                                assert the                                                                    activity                                                                      pin to the                                                                    EXPACT input                                                                  of the system                                                                 controller which                                                              will wake up the                                                              system                                                                  ______________________________________                                    

Upon expiration of a timer, the wireless interface device 100 entersinto an internal state "suspend" mode 165. In a suspend mode, thewireless interface device 100 is essentially turned off andcommunication packets from the host computer 101 are not handled. Thewireless interface device 100 emerges from suspend state 165 into activestate 161 when a pen event is detected.

As mentioned above, the video controller 113A supports various powermanagement modes internal to the display subsystem 113. Power isconserved in display subsystem 113 by entering "standby" and "suspend"modes. In the video controller 113A's "standby" mode, which can beentered by (i) expiration of a timer internal to the video controller113A, (ii) firmware in the video controller 113A, or (iii) a signalreceived from system controller 129 on the video controller 113A's"STANDBY" pin. In the video controller 113A's standby mode, the LCD 113Cis powered down and the video clock is suspended. The video controller113A exits the standby mode either under firmware control, or uponsystem controller 129's de-asserting video controller 113A's STANDBYpin. Upon exiting standby mode, the LCD 113C is powered and the videoclock becomes active. In this implementation, the LCD 113C includesmultiple power planes ("panels"). For reliability reasons, in a poweringup or powering down operation, these panels in the LCD display arepreferably powered in a predetermined sequence specified by themanufacturer.

Maximum power is conserved in the display subsystem 113 when videocontroller 113A enters the "suspend" mode. The suspend mode can beentered either by asserting a signal from the system controller 129 onthe SUSPEND pin of video controller 113A, or under firmware control. Inthis implementation, if the suspend mode is entered front the SUSPENDpin, the CPU 112 is prevented from accessing the video RAM 113B andvideo bus 113D. In that state, the contents of configuration registersin the video controller 113A are saved, to be restored when suspend modeis exited. In the suspend mode, the video RAM 113B is refreshed usingthe lowest possible refresh clock rate.

4. General Description of Operation

FIG. 6 is a block diagram illustrating the operational states ofwireless interface device 100 under the control of the Viewer Managersoftware 200. As shown in FIG. 6, on power up, the wireless interfacedevice 100 enters into a "TABLET SECURITY" state 201, in which anoptional security step is performed. In the state 201, either the device100 automatically shuts off after an idle period or the user performs a"log on" procedure which, as a security measure, identifies andvalidates the user. Then, at decision point 202, the Viewer Managersoftware 200 then determines if a procedure to set up a communicationlink is preconfigured. If so, a communication link is establishedautomatically with the host computer 101 and the Viewer Manager software200 goes into the normal operation state 205, which is described infurther detail below. If a communication link is not preconfigured, amanual procedure is performed in state 203, in which the desired hostcomputer 101 is identified and connected. From state 203, either thedevice 100 automatically shuts off after an idle period or the usercontinues on and enters normal operation state 205.

In normal operation state 205, the wireless interface device 100controls the program running in the host computer 101, in accordancewith the input data received from stylus input subsystem 110. Thepositions of the stylus in stylus input subsystem 110 are delivered tothe host computer 101, which generates display commands to the wirelessinterface device 100. The CPU 112 executes the display commandsreceived, which may result in an update of the LCD 113C. In thisembodiment, either a direct user command or inactivity over apredetermined time period causes the wireless interface device 100 toenter a "HOT-STANDBY" minimum power state ("sleep" mode), represented inFIG. 6 by block 204. In the minimum power state 204, to preserve batterypower, the various operations of the wireless interface device 100'sfunctional units are placed on standby status. If the status is put incontact with the digitizer panel, the wireless interface device 100 isreactivated, and control of the host computer 101 is resumed byre-entering state 205. Thereupon, wireless interface device 100 entersinto a state 206, in which an auto-disconnect procedure is executed,which releases control of the host computer 101 and powers down thewireless interface device 100.

The user may also relinquish control of the host computer 101 from state205 by selecting a manual disconnect function. When the manualdisconnect function is selected, the wireless interface device 100enters manual disconnect state 207, in which the connection to the hostcomputer 101 is terminated. The wireless interface device 100 is thenreturned to state 201 to accept the next user validation.

FIG. 7 is a block diagram of the software environment 240 in which thewireless interface device 100 and the host computer 101 operate toprovide the wireless interface device 100 remote control of the hostcomputer 101. As shown in FIG. 7, a wireless communication system 250 isprovided for communication between the host computer 101 and thewireless interface device 100. On the side of the wireless interfacedevice 100, i.e. software environment 230A, a communication outputmanager software routine 252 controls transmissions of pen events overthe wireless communication link 250 to a host communication inputmanager 262 in the host computer 101 (i.e. software environment 230B).The pen events include the position information of the stylus and tip-upand tip-down information. A pen event buffer 251 queues the pen eventsfor transmission through a communications manager 252. In the softwareenvironment 230A, the communications input manager 254 receives from thewireless communication system 250 video events transmitted by hostcommunication output manager 260 in the software environment 230B. Thesevideo events include graphical commands for controlling the LCD 113C. Inthe software environment 230A, the received video commands are queued inthe video event buffer 256 to be processed by the CPU 112 as graphicalinstructions to the LCD 113C.

In the software environment 230B, i.e. in host computer 101, pen eventsare queued in pen event buffer 264, which may then be provided to thePen Windows module 266. The Pen Windows module 266 processes the penevents and creates video events in a video event buffer 267, which isthen transmitted to the wireless interface device 100 over wirelesscommunication system 250.

FIG. 8 is a block diagram which shows in further detail the softwareenvironment 230B (FIG. 7) in the host computer 101; running anapplication program 270 under a Windows operating system 272. As shownin FIG. 8, the pen events queued in the pen event buffer 264 areprovided to a pen event injector 274, which provides the pen events fromthe pen event buffer 264, one pen event at a time, to a buffer ("RCbuffer") 275 of the Recognition Context Manager module (the "RCmanager") 276 in Pen Windows. The RC buffer 275 holds a maximum of fourpen events. The RC Manager 276 assumes that pen events are received atRC buffer 275 as they occur. Thus, if the Pen Windows system ispresented with pen events faster than they are retrieved from RC buffer275 without pen event injector 274, the pen events that arrive at RCbuffer 275 when it is full are lost. The pen event injector 274 preventssuch data loss. To provide this capability, the pen event injector 274includes both Windows virtual device (VxD) and device driver (DRV) codes(not shown). The DRV portion removes a single pen event from pen eventbuffer 264 and delivers it to the RC buffer 275 using the normal PenWindows add and process pen event mechanisms. Then the VxD portionreactivates the DRV code after a minimum time delay using a virtualmachine manager service to retrieve the next pen event from pen eventbuffer 264. Those of ordinary skill in the art would appreciate that,under the terminology used in Windows, DRV code refers to a dynamicallylinked library in Windows which interacts with a hardware device (inthis case, pen device buffer 264), and VxD code refers to a dynamicallylined library which manages a sharable resource (in this case, the DRVcode).

The RC Manager 276 examines each pen event in the RC buffer 275, andaccording to the context of the pen event in its possession, the RCManager 276 determines whether the stylus is in the pen mode or in themouse mode. In this embodiment, as will be discussed in more detailbelow, an icon allows the user to use the stylus as a "mouse" device.The icon, called "mouse button toggle", allows the user to switchbetween a "left" button and a "right" button as used in an industrystandard mouse device. The selected button is deemed depressed when thestylus makes contact with the pressure-sensitive digitizer panel. Arapid succession of two contacts with the display is read by the RCManager 276 as a "double click", and dragging the stylus along thesurface of the display is read by the RC Manager 276 as the familiaroperation of dragging the mouse device with the selected buttondepressed.

If the stylus is in the pen mode, the RC Manager 276 provides the penevent to a recognizer 277 to interpret the "gesture". Alternatively, ifthe pen event is a mouse event, the RC Manager 276 provides the penevent as a mouse event for further processing in a module 278. Theinterpreted gestures or mouse events are further processed as input dacato the Windows operating system 272 or the application program 270.

The output data from an application program, such as Windows 272 orapplication program 270, is provided to the video event buffer 267.These video events are transmitted to the host communications outputmanager 260 for transmission to the wireless interface device 100.

FIG. 9 is a block diagram which shows in further detail the softwareenvironment 230A in the wireless interface device 100 in the normaloperation state 205 of the Viewer Manager 200. In FIG. 9, the stylus inthe stylus input subsystem 110 and LCD video display 113C in the videodisplay subsystem 113 are shown collectively as a digitizer-displaydevice 279. In a normal operation state 205, the Viewer Manager 200interacts with the application program 270 in the wireless interfacedevice 100 by way of the Communications Output Manager 252 and theCommunications Input Manager software 254. In addition, the ViewerManager software 200 also receives digitized data from a digitizer 280,which, in turn, receives digitized data from stylus input subsystem 110.The Viewer Manager software 200 uses the digitized data to providevisual feedback to the user, which is discussed in further detail below.The Viewer Manager software 200 generates local video commands to adisplay driver 281. The display driver 281 also receives from videoevent buffer 256 video display commands from the host computer system101.

At the core of the wireless interface device 100's user interface is thestylus's behavior under Pen Windows. Of significance in wirelessinterface device 100's design is the emulation of the natural"pen-and-shaper" interaction with the user. That is, in a pen mode, thestylus must leave ink as it moves across the surface of the screen inthe same way that a pen leaves ink on paper. However, using Pen Windowssoftware, the RC Manager 276, residing in the host computer 101,determines for each pen event whether the mouse or the pen mode is used.

If the wireless interface device 100 simplistically accesses the hostcomputer 101 as a local device access, the wireless link between thehost computer 101 and the wireless interface device 100 would berequired to carry a minimum of 200 inking messages per second (100stylus tip locations plus 100 line drawing commands). To maintain thepen-and-paper emulation, the wireless interface device 100 is furtherrequired to have a total processing delay (hence response time),including the overhead of the communication protocols, which is near orbelow the human perception level. In addition, noise in the transmissionmedium often leads to momentarily interruption of data transmission, orresults in data corruption that requires re-transmission, therebyfurther reducing the throughput of the wireless link. To provide anacceptable level of performance, i.e., a high message-per-secondcommunication rate and an acceptable propagation delay, a techniquereferred to as "local inking" is developed and applied to the wirelessinterface device 100's design, in accordance with the present invention.Without local inking, a high bandwidth communication link is required tomeet the propagation delay requirement. Such a high bandwidthcommunication link is impractical, both in terms of cost and its impacton the portability of the resulting wireless access device.

With local inking, the Viewer Manager software 200 provides inking onthe LCD 113C locally before the corresponding inking video events arereceived from the host computer 101. In this manner, visual feedback isprovided virtually immediately without requiring either highly complexnetworking equipment, or very high performance and costly components inboth the wireless interface device 100 and the host computer 101. Localinking provides both a real time response and an orderly handling of thestylus's data stream. Since local inking reduces the need for processingat the peak pen event rate of the stylus's data stream, the hostcomputer 101 can thus apply normal buffering techniques, therebyreducing the bandwidth requirement on the communication network.

In one proposed industry standard for a stylus or pen-based system,namely the Microsoft Windows for Pen Computing system ("Pen Windows"),the pen mode requires (i) a pen driver that can deliver stylus tiplocations every five to ten milliseconds (100 to 200 times per second),so as to achieve a resolution of two hundred dots per inch (200 dpi),and (ii) a display driver than can connect these dots in a timelymanner. By these requirements, Pen Windows attempts to provide a realtime response to maintain the pen paradigm. The Windows for PenComputing system is promoted by Microsoft Corporation, Redmond, Wash.Details of the Pen Windows system are also provided in Windows version3.1 Software Developer Kit obtainable from Microsoft Corporation. Underone implementation of the Pen Windows, a maximum of four styluslocations can be stored in a buffer of a module called "PENWIN.DLL" (for"Pen Window Dynamically Linked Library"). Consequently, in thatimplementation, the maximum latency allowed is twenty to fortymilliseconds before any queue tip location is written. Each time thesystem fails to process a pen event within twenty to forty millisecondsof queuing, a stylus tip location is lost and there is a correspondingimpact on the accuracy of the line being traced.

As mentioned above, the stylus is used in both pen mode and mouse mode.Since the RC Manager 276, running on the host computer 101, rather thana software module on the wireless interface device 100, determineswhether a given pen event is a mouse mode event or a pen mode event, theViewer Manager software 200 must anticipate which of these modes isapplicable for that pen event. Further, should the anticipated modeprove to be incorrect, the Viewer Manager software 200 is required tocorrect the incorrectly inked image in video display subsystem 113.

FIG. 10 illustrates the method used in the wireless interface device 100to anticipate the RC Manager 276's mode decision and to correct theimage in the video display subsystem 113 when a local inking erroroccurs. As shown in FIG. 10, when the normal operational state 205 isentered, a pen control program (represented by the state diagram 282) inthe Viewer Manager software 200 is initially in the mouse mode in state283. However, even in the mouse mode, the trajectory of the stylus incontact with the pen digitizer is stored in the pen event buffer 284until a mode message is received from the host computer 101. The penevent buffer 284 is separate from pen event buffer 251, which is used totransmit the pen events to the host computer 101. If the RC Manager 276confirms that the stylus 110 is in a mouse mode, the accumulated penevents are discarded and the pen control program 282 waits for the lastpoint on which the pen tip is in contact with the pen digitizer. Thenthe pen control program 282 returns to a state 283, in which thetrajectory of the pen is again accumulated in the pen event buffer 284until receipt of a mode message from the host computer 101. In state283, the control program 282 assumes that the stylus will continue to bein the mouse mode.

Alternatively, while in state 283, if a mode message is receivedindicating the stylus is in the pen mode, the control program 282 entersstate 288, in which the accumulated pen events are drawn locally ontothe LCD screen of the video display subsystem 113 in accordance with theline style and color specified in the mode message. After allaccumulated pen events in the pen event buffer 284 are drawn, thecontrol program 282 enters a state 289, in which control program 282continues to ink the trajectory of the tip of the stylus for as long ascontact with the pen digitizer is maintained. Once the tip of the stylusbreaks contact with the pen digitizer, the control program 282 entersstate 287.

In state 287 the control program 282 assumes that the stylus willcontinue to be in the pen mode. Thus, local ink will follow thetrajectory of the stylus while the top of the stylus remains in contactwith the pen digitizer, or until a mode message is received from thehost computer 101, whichever arrives earlier. Since the initial policydecision is a guess, the local inking is drawn using a single pixel-widestyle and an XOR ("exclusive OR") operation, in which the pixels alongthe trajectory o)f the stylus are inverted. While in state 287, the penevents associated with the trajectory of the stylus are accumulated inthe pen event buffer 284.

If the mode message received in state 287 indicates that the stylus isin mouse mode, i.e. the policy decision was wrong, the control program282 then enters a state 290, in which the accumulated pen events in penevent buffer 284 are used to erase the stylus stroke. Since the initialdraw is accomplished by a bit XOR ("exclusive OR") operation at theappropriate positions of the frame buffer, erasure is simply provided bythe same XOR operation at the same positions of the frame buffer. Thecontrol program 282 then enters state 286. However, if the mode messagereceived in state 287 confirms that the stylus is in pen mode, theaccumulated pen events of pen event buffer 284 are used tc redraw on theLCD 113C, using the line style and color specified on the mode message.

Under a convention of the Pen Windows software, starting a stroke of thestylus with the barrel button depressed (for active stylus systems)indicates an erase ink operation in pen mode The control program 282recognizes this convention and refrains from inking during this strokewithout waiting for confirmation from the host computer 101. Inaddition, the control program 282 does not change modes across anerasing stroke: i.e., if the stylus is in the pen mode prior to theerase stroke, the stylus remains in the pen mode after the erase stroke;conversely, if the stylus is in the mouse mode prior to the erasestroke, the stylus remains in the mouse mode after the erase stroke.

Since all the pen events used in local inking on the wireless interfacedevice 100 are also processed in the host computer 101, the trajectoryof local inking must coincide identically with the line drawn at thehost computer 101. Because of local inking, processing by the hostcomputer 101 within the human perceptual response time is renderedunnecessary. Thus, in the host computer 101, the pen events can bequeued at pen event buffer 264, to be retrieved one at a time by penevent injector 274. Hence, when pen event buffer 264 is suitably sized,data loss due to overflow by RC buffer 275 is prevented.

Alternatively, the control program 282 can also be implemented to followa "retractable ball-point pen" paradigm Under this paradigm, the usercontrols a local stylus mode of the stylus, such that inking occurs whenthe stylus is set to be in the local pen mode, and no inking occurs whenthe stylus is 4n the local mouse mode. If the local stylus mode conformswith the mode expected by Pen Windows, the image seen on the LCD displayof the video display subsystem 113 is the same as described above withrespect to state 287 of the control program 282. If the local stylusmode is the mouse mode, and Pen Windows software expects stylus 110 tobe in the pen mode, the subsequent video events from host computer 101would provide the required inking. Finally, if the local stylus mode isthe pen mode and Pen Windows software expects the stylus to be in themouse mode, inking would be left on the screen of video displaysubsystem 113. Under this paradigm, the user would eliminate theerroneous inking by issuing a redraw command to Pen Windows.

5. Detailed Description of the Schematic Diagrams

One embodiment of the invention is illustrated in the schematicdrawings, FIGS. 11-30. Referring to FIG. 11, the system may include aCPU 112, such as an AMD Model No. AM386DXLV microprocessor. The CPU 112includes a 32-bit data bus D[0..31] as well as a 32-bit address busA[2..31]. Both the data bus D[0..31] as well as the address bus A[2..31]are connected to the processor bus 150 (FIG. 4), for example, an AT bus.As will be discussed in more detail below, the system controller 129(FIG. 4) performs various functions including management of theprocessor bus 150. In order to conserve power, a 3-volt microprocessormay be used for the CPU 112. As such, a 3-volt supply 3 V CPU is appliedto the power supply VCC pins on the CPU 112. The 3-volt supply 3 V₋₋ CPUis available from a DC-to-DC converter 300 (FIG. 26) by way of a ferritebead inductor 302. In particular, the DC-to-DC converter 300 includes a3-volt output, 3 V₋₋ CORE. This output, 3 V₋₋ CORE, is applied to theferrite bead inductor 302 and, in turn, to the power supply pins VCC ofthe CPU 112. In order to prevent noise and fluctuations in the powersupply voltage from affecting the operation of the CPU 112, the powersupply voltage 3 V CPU is filtered by a plurality of bypass capacitors304 through 330.

The 3-volt supply 3 V₋₋ CPU is also used to disable unused inputs aswell as to pull various control pins high for proper operation. Forexample, the 3-volt power supply 3 V₋₋ CPU is applied to the active lowN/A and BS16 pins of the CPU 112 by way of a pull-up resistor 332. Inaddition, the signals BE[0..3], WIR, D/C, M/IO and ADS are pulled up bya plurality of pull-up resistors 334 through 348.

The CPU 112 is adapted to operate at 25 megahertz (Mz) at 3.0 volts. A25 MHz clock signal, identified as CPU CLK, available from a clockgenerator 398 (FIG. 13), is applied to a clock input CLK2 on the CPU 112by way of a resistor 348 and a pair of capacitors 351 and 353. The AMDModel No. AMD386DXLV microprocessor supports a static state, whichenables the clock to be halted and restarted at any time.

The wireless interface device 100 includes a speaker 355. The speaker355 is under the control of the system controller 129 (FIG. 12). Inparticular, a speaker control signal SPKR from the system controller 129is applied to a source terminal of a field-effect transistor (FET) 357for direct control of the speaker 355. The drain terminal is connectedto the speaker 355 by way of a current-limiting resistor 359 and abypass capacitor 371. Normally, the speaker 355 is active all the time.In particular, the gate terminal of the FET 357 is connected to thesystem ground by way of a resistor 373. The gate terminal of the FET 357is also under the control of a speaker disable signal SPKRDISABLE,available from the keyboard controller 125 (FIG. 15). The speakerdisable signal SPKRDISABLE is active high. Thus, when the speakerdisable signal SPKRDISABLE signal is low, the FET 357 is turned on toenable the speaker signal SPKR from the system controller 129 to controlthe speaker 355. When the speaker disable signal SPKRDISABLE is high,the FET 357 is turned off to disable the speaker 355.

Referring to FIG. 12, the system controller 129 is connected between thelocal processor or AT bus 150 and the system ISA bus 151. The systemcontroller 129 performs a variety of functions including that of systemcontroller, DRAM controller, power management, battery management andmanagement of the local AT bus 150. The system controller 129,preferably a PicoPower Pine Evergreen 3, Model No. 86C368 systemcontroller, is a 208-pin device that operates at 33 MHz with a full5-volt input or a hybrid 5-volt/3.3 volt input. At 3.3 volts the systemcontroller 129 is adapted to reliably operate at 20 Mhz and perhaps upto 25 Mhz.

The system controller 129 includes several system features includingsupport of several clock speeds from 16 to 33 MHz. In addition, thesystem controller 129 includes two programmable non-cacheable regionsand two programmable chip selects, used for universal asynchronousreceiver transmitter (UART) interface 134 and the radio interface 114Bas discussed below.

The system controller 129 supports both fast GATE A20 and a fast resetcontrol of the CPU 112. In particular, the system controller 129includes a 32-bit address bus A[0..31] that is connected to the local ATbus 150. The address line A[20] is used to develop a signal CPUA20,which is applied to the A20 pin on the CPU 112 and also applied to anAND gate 379 (FIG. 11) to support a port 92 H for a fast GATE A20 signalA fast reset signal RSTCPU is also generated by the system controller129. The fast reset signal RSTCPU is applied to the reset oin RESET ofthe CPU 112 for fast reset control.

The system controller 129 also provides various other system levelfunctions. For example, the system controller 129 includes a register ataddress 300 H. By setting bit 12 of this registers a ROM chip selectsignal ROMCS is generated, which enables writes to the flash memorysystem 117 (FIG. 25), which will be discussed below. A keyboardcontroller chip select signal KBDCS for the keyboard controller 125(FIG. 15), as well as general purpose chip select signals GPCS1 andGPCS2 for selecting between the RF controller 114A, the UART 134 (FIG.16) or the pen controller 110A (FIG. 21), are generated by the systemcontroller 129.

The system controller 129 is connected to the system ISA bus 151 by wayof a 16-bit system data bus SD[0..15] and a 24-bit system address busSA[0..23] of which only 8-bits SA[0..7] are used. The system controller129 is also connected to the 32-bit local processor data bus D[0..31],as well as the local processor address bus A[0..31].

All of the ground pins GND on the system controller 129 are tied to thesystem ground. Both 3-volt and 5-volt power supplies are applied to thesystem controller 129. In particular, a 5-volt supply 5 V₋₋ EG isapplied to the power supply pins VDD of the system controller 129. The5-volt supply 5 V₋₋ EG is available from DC-to-DC converter 300 (FIG.26) by way of a ferrite bead inductor 381 (FIG. 12). More particularly,a 5-volt supply signal 5 V₋₋ CORE from the DC-to-DC converter is appliedto the ferrite bead inductor 381, which, in turn, is used to generatethe 5-volt supply signal 5 V₋₋ EG. In order to stabilize the 5-voltsupply signal 5 V₋₋ EG, a plurality of bypass capacitors 1101-1111 (FIG.13) are connected between the 5-volt supply 5 V₋₋ EG and system ground.

A 3-volt power supply 3 V₋₋ EG is also applied to the system controller129 and, in particular, to the power supply pins VDD/3 V. This 3-voltsupply 3 V₋₋ EG is also obtained from the DC-to-DC converter 300 (FIG.26) by way of a ferrite bead inductor 358. More particularly, 3-voltsupply 3 V₋₋ CORE, available at the DC-to-DC converter 300, is appliedto the ferrite bead inductor 358, which, in turn, is used to generatethe 3-volt power supply signal 3 V₋₋ EG. A plurality of bypasscapacitors 360, 362 and 364 are connected between the 3-volt supply 3V₋₋ EG and system ground for stabilizing.

The system controller 129 is reset by a reset signal RCRST (FIG. 20) onpower up. The reset signal RCRST is developed by the 3-volt power supply3 V₋₋ EG, available from the DC-to-DC converter 300 (FIG. 26) andcircuitry which includes a resistor 359, a capacitor 361 and a diode363. Initially on power up, the capacitor 361 begins charging up fromthe 3-volt supply 3 V₋₋ EG through the resistor 359. During this state,the diode 363 is non-conducting. As the capacitor charges, the level ofthe reset signal RCRST rises to reset the system controller 129. Shouldthe system be turned off or the 3-volt supply 3 V₋₋ EG be lost, thediode 363 provides a discharge path for the capacitor 361.

In order to assure proper operation of the system controller 129, anumber of signals are pulled up to either five volts or three volts orpulled down by way of various pull-down resistors. More specifically,the signals IOCS16, MASTER, MEMCS16, REFRESH, ZWS, IOCHCK, GPI01/MDDIRand GPI02/MDEN are pulled up to the 5-volt supply 5 V₋₋ EG by way of aplurality of pull-up resistors 1113-1129, respectively. Similarly, thesignals BUSY, FERR, LOCAL, SMIADS and RDY are pulled up by a pluralityof pull-up resistors 1131 through 1139. In addition, the general purposechip select signals GPCS1 and GPCS2 are pulled up to the 5-volt powersupply signal 5 V₋₋ EG by way of a pair of pull-up resistors 375 and377. Certain signals are pulled low by way of pull-down resistors inorder to assure their operating state. In particular, the signalsKBC-PO4, LB/EXTACT, RING, EXTACT/VLCLK and HRQ206 are pulled down by thepull-down resistors 388 to 396. The signal BLAST is tied directly to thesystem ground.

As mentioned above, the system controller 129 is capable of running atdifferent clock frequencies, depending upon the voltage applied, whilesupplying a clock signal to the CPU 112. Even though the systemcontroller 129 can supply either a 1X or a 2X clock signal to the CPU112, the system controller 129 requires a 2X clock for proper operation.Thus, a 2X clock signal CLK2IN, available from a clock generator circuit398 (FIG. 13); is applied to the clock 2X pin CLK2IN of the systemcontroller 129. In addition, 32 kilohertz (KHz) and 14 megahertz (MHz)clock signals are also applied to the system controller 129, availablefrom the clock generator circuit 398, for proper operation. The systemcontroller 129, in turn, provides a CPU clock signal CPUCLK to the CPU112 and in particular to its clock 2-pin CLK2 by way of a resistor 1141and the capacitors 1143 and 1145.

The system controller 129 is adapted to be configured during an RC-RESETmode. In particular, the DRAM memory address lines MA[0..10], normallyused for addressing the DRAM 111A (FIGS. 18 and 24), are pulled high orlow in order to configure the system controller 129. More particularly,the DRAM memory address lines MA[0..10] are applied to either pull-up orpull-down resistors for configuration as illustrated in FIG. 17. Table 2below illustrates the configuration shown.

                  TABLE 2                                                         ______________________________________                                        System Controller Configuration Table                                           NAME      FUNCTION          DEFAULT STATE                                   ______________________________________                                        MA0     386 Select (Low = 46)                                                                           High                                                  MA1 Low Power Select (High Low                                                 Selects Intel LP CPU,                                                         Low For Other)                                                               MA2 1X CPU Clock Select Low                                                    Low = 2X CPU CLK                                                             MA3 Not Used Low                                                              MA4 Not Used Low                                                              MA5 368 Pin Select (Low = High                                                 pin compatible with 268)                                                     MA6 Miscellaneous Low                                                          Configuration - 0                                                            MA7 Not Used High                                                             MA8 Not Used Low                                                              MA9 Not Used Low                                                              MA10 Not Used Low                                                           ______________________________________                                    

As shown, the DRAM memory address lines MA[0..10] are shown with bitsMA0, MA5 and MA7 pulled high to the 3-volt power supply voltage 3 V₋₋ EGby way of a plurality of pull-up resistors 400, 402 and 404. Theremaining DRAM address line bits MA1, MA2, MA3, MA4, MA6, MA8, MA9 andMA10 are pulled low by a plurality of pull-down resistors 406 through420, respectively. The DRAM memory address lines MA[0..8] are alsocoupled to a plurality of coupling resistors 422 to 438 form a 9-bitDRAM address bus BMA[0..8].

The system controller 129 functions as a DRAM controller and is capableof supporting up to 64 megabytes of memory, divided among one of fourbanks and can support 256K, 512K, 1M, 2M and 4M of memory in any width.The system controller 129 includes a pair of registers associated witheach bank of DRAM. The first register stores the total amount of DRAMconnected to the system while the second identifies the starting addressfor each bank. Referring to FIGS. 18 and 24, two 1 Mbyte banks areconnected to the DRAM memory address bus BMA[0..8] and to the processordata bus 150, D[0..31].

In order to conserve power, 3-volt DRAM 111A is used. The 3-volt powersupply 3 V₋₋ RAM is applied to the VCC terminals of each of the DRAMS111A. The 3-volt power supply 3 V₋₋ RAM is available from the DC-to-DCconverter 300 (FIG. 26) by way of a ferrite bead inductor 440 (FIG. 18).In particular, a 3-volt supply 3 V₋₋ CORE available at the DC-to-DCconverter 300 is applied to the ferrite bead inductor 440 to generatethe 3-volt DRAM supply 3 V₋₋ RAM. A plurality of bypass capacitors425-439 (FIG. 18) are connected between the DRAM supply voltage 3 V₋₋RAM and system ground.

The system controller 129 generates the appropriate row address strobes(RAS) and column address strobes for the DRAM 111A. In particular, thecolumn address strobe lines CAS0[0..3] are applied to the upper andlower column address strobe pins (UCAS and LCAS) on the DRAM 111A by wayof a plurality of coupling resistors 442 to 450 (FIG. 12). Similarly,the row address signals RAS0 and RAS1 are applied to the row addressstrobe pins on the DRAM 111A by way of a plurality of coupling resistors448 and 450. Writing to the DRAMS 111A is under the control of a DRAMwrite enable signal BRAMW, applied to the write enable pin WE on theDRAM 111A. The DRAM write enable signal BRAMW is generated by the systemcontroller 129 by way of a coupling resistor 452.

An EEPROM or NVRAM 111B (FIG. 12) may be used to maintain systemconfiguration parameters when the system is powered off. All userchangeable parameters are stored in the EEPROM 111B. For example, pencalibration data and passwords, used during boot up, may be used in theEEPROM 452. The contents of the EEPROM 111B may be shadowed into a CMOSmemory when the system is active Communication with the EEPROM 111B isunder the control of the system controller 129 and in particular, a pairof programmable input/output pins GPI01 and GPI02. The GPI01 provides aclock signal to the EEPROM 111B while the pin GPI02 is used for datatransfer.

As discussed above, the wireless interface device 100 also includes theflash memory 117 (FIG. 25), which is used for storing the BIOS. Thesystem controller 129 allows for direct shadowing of the BIOS byenabling the appropriate address space to read the FLASH/DRAM write modewhich allows all reads to come from the flash device with writes to theDRAM 111A memory devices.

A main memory map as well as an I/O memory map are provided in Tables 3and 4.

                  TABLE 3                                                         ______________________________________                                        Main Memory Map                                                               ______________________________________                                         ##STR1##                                                                     ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        I/O MEMORY MAP                                                                  Memory Space Description                                                                           Memory Locations (HEX)                                 ______________________________________                                        DMA Controller #1  00 - 0F                                                      Not Used 10 - 1F                                                              Interrupt Controller #1 20 - 21                                               Not Used 22 - 23                                                              Evergreen Configuration Address 24                                            Not Used 25                                                                   Evergreen Configuration Data 26                                               Not Used 27 - 3F                                                              Counter/Timer 40 - 43                                                         Not Used 44 - 5F                                                              Keyboard Controller 60                                                        Port B 61                                                                     Not Used 62 - 63                                                              Keyboard Controller 64                                                        Not Used 65 - 6F                                                              NMI Enable, Real-Time Clock 70, 71                                            Not Used 72 - 7F                                                              DMA Page Registers 80 - 8F                                                    Not Used 90 - 91                                                              Port A 92                                                                     Not Used 93 - 9F                                                              Interrupt Controller #2 A0 - A1                                               Not Used A2 - CF                                                              DMA Controller #2 D0 - DE                                                     Not Used DF - 2FF                                                             Pen Controller 300                                                            Not Used 301 - 3AF                                                            Graphics Controller 3B0 - 3DF                                                 RF Controller 3E0 - 3E7                                                       UART COM1 3E8 - 3EF                                                           Not Used 3F0 - 3FF                                                          ______________________________________                                    

In addition to system control features and DRAM control, the systemcontroller 129 provides various other functions. The power managementfunction and NVRAM controller have been discussed above. The systemcontroller 129 also controls all operations on the local AT bus 150. TheAT bus clock is derived from the clock CLK2IN pin that is divided toachieve an 8 MHz bus rate.

The system controller 129 also includes a number of programmable pinswhich enhance its flexibility. For example, four general purposeinput/output pins GPIO[0..3] are provided; each of which may beindependently set for input or output. The GPIO1 and GPIO2 pins are usedfor the EEPROM 1111 as discussed above. The GPIO0 pin and GPIO3 pin maybe used for various purposes. In addition to the programmableinput/output pins, the system controller 129 includes two generalpurpose chip select pins GPCS1 and GPCS2 as well as a plurality ofprogrammable output pins PC[0..9]. The programmable chip selects GPCS1and GPCS2 are used for the pen controller 110A, UART 134 and the radiointerface 114B.

Peripheral devices connected to the system ISA bus 151 are controlled byan integrated peripheral controller 128 as discussed above. Theintegrated peripheral controller 128 may be a PicoPower Model No.PT82C206F which can be operated at either 3.3 or 5 volts As will bediscussed in more detail below, the integrated peripheral controller 128includes several subsystems such as: DMA Control; Interrupt Control;Timer Counter; RTC Controller; CMOS RAM and Memory Mapper.

The IPC 128 includes two type 8259A compatible interrupt controllerswhich provide 16 channels of interrupt levels, one of which is used forcascading. The interrupt controller processes all incoming interrupts inorder as set forth in Table 5.

                  TABLE 5                                                         ______________________________________                                        INTERRUPT TABLE                                                                    INTERRUPT      DESCRIPTION                                               ______________________________________                                        Level 0         Timer Channel 0                                                 Level 1 Keyboard Controller 2 Cascade                                         Level 2 Second Interrupt Controller                                           Level 3 Not Used                                                              Level 4 COM1                                                                  Level 5 Pen Controller                                                        Level 6 Not Used                                                              Level 7 Not Used                                                              Level 8 RTC Controller                                                        Level 9 Not Used                                                              Level 10 Radio Controller                                                     Level 11 Not Used                                                             Level 12 Not Used                                                             Level 13 Not Used                                                             Level 14 Not Used                                                             Level 15 Not Used                                                           ______________________________________                                    

The integrated peripheral controller (IPC) 128 (FIG. 14) is connected tothe system data bus SD[0..15]. Addressing of the IPC 128 is accomplishedby two bits SA0 and SA1 from the system address bus SA[0..23] and eightbits A[2..9] from the local address bus A[0..31] The address bits fromthe local address bus A[2..8] are converted to 5 volts by way of a 3- to5-volt signal converter 453 (FIG. 14) to develop the 5-volt addresssignals XA[2..8]. A 32-kilohertz clock signal 32-KHz from the clockgenerator 398 (FIG. 13) is applied to the clock input OSC1 of the IPC128.

Referring to FIG. 20, in order to prevent spurious operation of the IPC128 before the system power supply is stabilized, a power good signalPWRGOOD is applied to a power good pin PWRGD. The power good signalPWRGOOD is a delayed signal which assures that the 5-volt power supplyhas stabilized before the IPC 128 is activated. In particular, a 5-voltpower supply 5 V₋₋ CORE is applied to a delay circuit which includes aresistor 454, a diode 456 and a capacitor 458. Initially, the 5-voltpower supply signal 5 V₋₋ CORE is dropped across the resistor 454. Whilethe capacitor 458 is charging, the diode 456 is in a non-conductingstate. As the capacitor 458 begins to charge, the voltage at the anodeof the diode 456 increases as a function of the RC time constant. Whenthe capacitor 458 is fully charged, it approaches the value of the powersupply voltage 5 V₋₋ CORE. When the capacitor 458 becomes fullycharge-d, the power good signal PWRGOOD is applied to a power good pinPWRGD at the IPC 128 for enabling the IPC 128 after the power supply hasstabilized. The diode 456 provides a discharge path for the capacitor458 when the power supply is shut off. The power good signal PWRGOOD isalso used to reset the keyboard controller 125.

A 5-volt power supply 5 V₋₋ CORE from the DC-to-DC converter 300 (FIG.26) is applied to a ferrite bead inductor 460 (FIG. 13) to develop a5-volt power supply 5 V₋₋ 206, which, in turn, is applied to the powersupply pins VCC of the IPC 128. In order to delay application of the5-volt power supply 5 V₋₋ 206 as discussed below, a charging circuitwhich includes a serially coupled resistor 462 and a capacitor 464 areconnected between the power supply voltage 5 V₋₋ and the system ground.A power supply reset signal PSRSTB, an active low signal, is applied tothe junction between the resistor 462 and the capacitor 464 to dischargethe capacitor 464 when the power supply is reset. Moreover, in order tostabilize the voltage of the power supply 5 V₋₋ 206, a plurality ofbypass capacitors 466 and 468 are connected between the power supply 5V₋₋ 206 and system ground.

In order to assure proper operation of the circuit, various pins of theIPC 128 are pulled low while various other pins are pulled high. Inparticular, the input/output read and write signals IOR and IOW arepulled up to the power supply voltage 5 V₋₋ 206 by a pair of pull-upresistors 470 and 472. In addition, the interrupt request pin IRQ10 ispulled up to the power supply voltage 5 V₋₋ CORE by a pull-up resistor474. The signals OUT2, REFREQ, AEN16 and AEN8 are pulled low bypull-down resistors 455-461 while the signal TEST₋₋ MODE2 is pulled upto the supply voltage 5 V₋₋ CORE by a pull-up resistor 463.

Even though the IPC 128 includes a direct memory access (DMA)controller, this function is not required by the system. As such, thedirect memory access request pins DREQ[0..7] are pulled low by apull-down resistor 476 to system ground. In addition, as set forth inTable 5 above, various interrupt levels are unused. For example, asshown in Table 5, interrupt levels IRQ3, IRQ6, IRQ7, IRQ9, IRQ11, IRQ12,IRQ14, and IRQ15 are not used. Thus, these interrupt levels are pulledlow by a pull-down resistor 478.

As illustrated in Table 5, interrupt levels IRQ4 and IRQ5 are used forthe COM1 and pen controller interrupt levels, IRQ4 and IRQ5. To assurethat these levels are proper, the IRQ4 and IRQ5, which are active high,are pulled low by pull-down resistors 480 and 482.

Interrupts by the system controller 129 and IPC 128 INTR₋₋ EG andINTR206 are applied to the CPU 112 by way of a diode 479 and pull-upresistor 481 (FIG. 14). In particular, the interrupt signals INTR₋₋ EGand INTR206 from the system controller 129 and IPC 128, respectively,are applied to the cathode of the diode 479 while the anode is pulled upto the power supply voltage 3 V₋₋ CORE by the pullup resistor 481 Thelogic level of the anode is set by the interrupt signal INTR, which isapplied to the CPU 112. When the interrupt signals INTR206 and INTR₋₋ EGare high, the diode 479 does not conduct and the CPU 112 interruptsignal INTR will be high. When either of the interrupt signals INTR₋₋ EGor INTR206 are low, the diode 479 conducts, forcing the CPU 112interrupt signal INTR low.

The IPC 128 also includes a type 8254 compatible counter/timer which, inturn, contains three 16-bit counters that can be programmed to count ineither binary or binary-coded decimal. The zero counter output is tiedinternally to the highest interrupt request level IRQ0 so that the CPU112 is interrupted at regular intervals. The outputs of the timers 1 and2 are available for external connection. In particular, internal timer 1generates one signal, OUT1, which is used to generate a DRAM refreshrequest signal REFREQ to the CPU 112. The internal timer 2 generates anoutput signal OUT2 that is used to generate speaker timing. All threeinternal timers are clocked from a timer clock input TMRCLK at 1.2megahertz from the system controller 129.

As mentioned above, the IPC 128 includes a real time clock (RTC)controller which maintains the real time. The real operational time ismaintained in a CMOS RAM that can be accessed through registers 70H and71H. The memory map for the CMOS memory is provided in Table 6 as shownbelow.

                  TABLE 6                                                         ______________________________________                                        CMOS MEMORY MAP                                                                       INDEX           FUNCTION                                              ______________________________________                                        00H                 Seconds                                                     01H Seconds Alarm                                                             02H Minutes                                                                   03H Minutes Alarm                                                             04H Hours                                                                     05H Hours Alarm                                                               06H Day of Week                                                               07H Day of Month                                                              08H Month                                                                     09H Year                                                                      0AH Registry                                                                  0BH Register B                                                                0CH Register C                                                                0DH Register D                                                                0EH-7EH User RAM                                                            ______________________________________                                    

The area designated as User RAM is used by the system BIOS to save thestatus of the system configuration registers. The alarm bytes may beused to set and generate an interrupt at a specific time. When periodicinterrupt is required, the two most significant bits in the alarmregister can be set high.

The various clock signals used for the system are provided by the clockgenerator circuit 398 (FIG. 13). The clock circuit 398 includes a clockgenerator, for example, an Integrated Circuit Designs Model No. ICD2028.A 14.318 MHz crystal 484 and a 32.768 KHz crystal 486 are applied to theclock generator 488. In particular, the crystal 484 is applied to a pairof X1 and X2 input pins along with a plurality of capacitors 489, 490,492 and an input resistor 494. Similarly, the crystal 486 is applied toinput pins XSYSB1 and XSYSB2. A pair of capacitors 496 and 498 areconnected across the crystal 486.

The clock generator IC 488 provides three clock outputs CLKA, CLKB andCLKD. The clock A output CLKA is used to develop an 8-MHz clock signalfor the keyboard controller 125 by way of a resistor 500 and capacitors502 and 504. The clock B output CLKB is used to develop a clock 2Xoutput signal CLK2IN for the system controller 129 by way the resistors506, 508 and 510 and a pair of capacitors 512 and 514. The clock Doutput signal CLKD is used to generate a 1.84 MHz signal for use by theUniversal Asynchronous Receiver Transmitter (UART) 134 by way of aresistor 516 and capacitors 518 and 520. As mentioned above, the systemcontroller 129 also requires a 14 MHz clock signal. This clock signal isdeveloped by way of a system bus output pin SYSBUS, a resistor 522 and apair of capacitors 524 and 526.

Selection of the various clock output signals is available by way of theselect pins S0, S1 and S2. These pins S0, S1 and S2 are pulled up to the3-volt power supply 3 V₋₋ CORE by way of pull-up resistors 521, 523 and525. The 3-volt power supply signal 3 V₋₋ CORE is available from theDC-DC converter 300 (FIG. 26).

The clock generator 488 utilizes a 3-volt power supply CLOCK₋₋ VCC (FIG.13). The 3-volt power supply CLOCK₋₋ VCC is available from the DC-to-DCconverter 300 (FIG. 26) by way of an in-line ferrite bead inductor 530.In particular, the 3-volt power supply 3 V₋₋ CORE is applied to theferrite bead inductor 530 to generate the power supply for the CLOCK₋₋VCC for the clock generator 488. This power supply CLOCK₋₋ VCC isapplied to the power supply pin VDD. The power supply signal CLOCK₋₋ VCCis also used as analog supply AVDD to the clock generator IC 488 and isapplied to the analog supply AVDD by way of the resistor 532 and a pairof capacitors 534 and 536. The power supply signal CLOCK₋₋ VCC is alsoapplied to the battery pin VBATT of the clock generator IC 488 by way ofa diode 537 to prevent any back feeding.

A number of the circuits in the system operate at either 3.3 volts or 5volts. Thus, a plurality of bi-directional signal level translators 542and 544 (FIG. 14) are provided, as well as the translator 453 previouslydiscussed. The signal level translators 453, 542 and 544 may be assupplied by Integrated Circuit Technology, Model No. FCT164245T. Each ofthe signal level translators 453, 542 and 544 includes a 3-volt supply 3V₋₋ CORE and a 5-volt supply 5 V₋₋ CORE, available from the DC-to-DCconverter 300 (FIG. 26) In order to stabilize the voltage of the 3- and5-volt power supplies, 3 V₋₋ CORE and 5 V₋₋ CORE, a plurality of bypasscapacitors are utilized. In particular, the bypass capacitors 546through 552 are connected between the 3-volt supply 3 V₋₋ CORE andsystem ground. Similarly, the bypass capacitors 554 through 560 areconnected between the 5-volt supply 5 V₋₋ CORE and system ground. Theground terminals of each of the signal level translators 542, 544 and453 are also tied to system ground.

Each of the signal level translators 542, 544 and 453 includes two 8-bitprogrammable input/output pins. More particularly, the first 8-bit group1A/1B[1..8] is under the control of an operate/enable pin 1OE, which isactive low, while the second bank 2A/2B[1..8] is under the control of anoutput/enable pin 2OE, also active low. The direction of the input pinsand output pins (i.e., A relative to B) is under the control ofdirection pins 1DIR and 2DIR. The direction pin 1DIR controls thedirection of the pins 1A/1B[1..8], while the pin 2DIR controls thedirection of the pins 2A/2B[1..8].

The signal level translator 453 is used to convert the local data busbits D[16..31] and the system data bus bits SD[0..15]. Both the localdata bus D[16..31] as well as the system data bus SD[0..15] arebi-directional. In this application the processor bus 150 data bitsD[31...16] are being mapped to the system data bus bits SD[15...0].

The direction of the signal level translator 542 is under the control ofa signal direction signal SDIR, available at the system controller 129.The signal direction signal SDIR is applied to both the directioncontrol pins 1DIR and 2DIR of the signal level translator 542. Theoperate/enable inputs 1OE and 2OE are under the control of system dataenable inputs signals, SDEN3 and SDEN2, respectively; also under thecontrol of the system controller 129.

The signal level translator 544 is used to map the signal levels of thelocal address bus bits A[23...8] to the system address bus bitsSA[23...8]. More particularly, the local address bits A[23..16] areapplied to pins 1A[1..8] while the local address bits A[15..8] areapplied to the pins 2A[1..8]. Similarly, the system address bitsSA[23..16] are connected to the pins 1B[1..], while the system addressbits SA[15..8] are applied to the pins 2B[1..8]. In this case, theoperate/enable pins 1OE and 2OE, both active low, are connected tosystem ground in order to permanently enable the signal level translator544. The direction control pins 1DIR and 2DIR are permanently set suchthat the data always flows from A to B. In particular, the directionalpins 1DIR and 2DIR are connected to the 3-volt power supply 3 V₋₋ COREby way of a pull-up resistor 562.

The signal level translator 542 is used to convert the signal levels ofthe 3-volt clock output signals 14 Mhz, 1.84 Mhz, 32 Khz and 8 Mhz to5-volt levels, as well as to convert the 3-volt local address bitsA[2..8] to 5-volt address bits XA[2..8] for use by the IPC 128, asdiscussed above. More particularly, the system address bits, A[2..8] areapplied to the pins 1A[1..8] The clock signals 14 MHz, 1.84 MHz, 32 KHzand 8 MHz are applied to the pins 2A1, 2A3, 2A6 and 2A8, respectively,to produce corresponding 5-volt level signals 14 MHz₋₋ 5 V, 1.84 MHz₋₋ 5V, 32 KHz₋₋ 5 V and 8 MHz₋₋ 5 V signals at pins 2B1, 2B3, 2B6 and 2B8,respectively. The unused pins 1A8 and 2B8 are pulled low by way ofpull-down resistors 564 and 565, respectively. The operate/enable pins1OE and 2OE are tied to system ground to permanently enable the signallevel translator 542. The directional pins 1DIR and 2DIR are pulled upto the 3-volt power supply voltage 3 V₋₋ CORE by way of a pull-upresistor 566 to permanently force the direction from A to B.

Referring to FIG. 15, the system includes a keyboard controller 125,which performs several functions, including battery monitoring, LCDstatus control, brightness and contrast control, as well as keyboardcontrol. In addition, the system also maintains the status of theremaining battery life, and also provides information to the systemcontroller 129 when the battery voltage is low or other critical batterycondition has occurred. In operation, the keyboard controller 125 willmaintain the current status of the battery level until data isrequested. When a critical battery condition event occurs, the keyboardcontroller 125 generates an SMI interrupt. As discussed above, theintelligent battery pack (IBP) 130 provides an indication of thepercentage of remaining battery capacity. Communication between the IBP130 and the keyboard controller 125 is by way of a bi-directional serialdata bus, which includes a clock line BATCLK and a data line BATDATA.The data line BATDATA is a bi-directional line, which allows forbi-directional communication with the IBP 130. The clock line BATCLK isdriven by the IBP 130, but may be pulled low by the keyboard controller125.

The bi-directional serial data bus is connected to the port pins P4.2and P4.3 on the keyboard controller 125. In particular, the port pinP4.2 is used for the serial battery data BATTDATA. An NPN transistor 570is connected to the port pin P4.2 to disconnect the keyboard controller125 from the IBP 130 during power down. In particular, the collectorterminal of the NPN transistor 570 is connected to the port pin P4.2,while the emitter terminal forms a battery data signal BATTDATA. Thebase of the NPN transistor 570 is biased on by way of a biasing resistor572 that is connected to a 5-volt power supply 5 V₋₋ KBD. The collectoris pulled high by way of a pull-up resistor 574 connected to the 5-voltpower supply 5 V₋₋ KBD.

Similarly, the battery clock signal BATTCLK is connected to the port 4.3on the keyboard controller 125 by way of an NPN transistor 576. Thecollector terminal of the NPN transistor 576 is connected to the port4.3 as well as to a pull-up resistor 578 and the 5-volt power supply 5V₋₋ KBD. The NPN transistor 576 is turned on anytime the power supply tothe keyboard 5 V₋₋ -KBD is powered up by way of a biasing resistor 580.The emitter of the NPN transistor 576 forms the battery clock signalBATTCLK.

In addition to battery management, the keyboard controller 125 alsosupports an external PS/2-type keyboard, as well as a PS/2-type bar codereader, connected to a keyboard connector 140 (FIG. 29). Communicationbetween the keyboard or bar code reader (not shown) is by way of astandard type PS-2 two-wire bus connected to serial ports P4.6 and P4.7.In particular, the keyboard data KDATA is pulled up to the 5-voltvoltage supply 5 V₋₋ CORE by way of a pull-up resistor 582 while thekeyboard clock signal KCLK is pulled up the 5-volt supply 5 V₋₋ CORE byway of a pull-up resistor 584.

Referring to FIG. 29, the keyboard connector 140 may be a 6-pin MINI-DINconnector or a DB-8 connector as shown. Pins 6-9 are connected to systemground. Pin 4 of the connector 140 is pulled up to the power supplyvoltage 5 V₋₋ CORE by way of a fuse 579 and is filtered by a capacitor581 and an inductor 583. The data signal KDATA is applied to pin 1 byway of a current-limiting resistor 585, while the clock signal KCLK isapplied to pin 5 by way of a current-limiting resistor 587 and a pair ofcapacitors 589 and 591. These clock and data signals KCLK and KDATA areconnected to the ports P4.6 and P4.7, respectively, for serialcommunication with an external keyboard or bar code reader.

Additionally, the keyboard controller 125 may be used to control thebrightness level as well as the contrast level of the LCD display. Moreparticularly, referring to FIG. 27, a contrast signal CONTRAST,available at port 0, pin 1 of the keyboard controller 125 (FIG. 15) isused to adjust the contrast level of the LCD display. The contrastsignal CONTRAST is applied to an adjustment terminal ADJ of a negative24-volt DC voltage supply, which can be incrementally adjusted in stepsby a 24-volt DC supply 586 (FIG. 27), for example, a Maxim Model No.749, which provides for 64-step adjustment. Thus, each high pulse willincrement the contrast of the LCD display by one step. With a 64-stepdevice, sixty-three pulses rolls the counter over and decreases thecontrast by 1. The 24-volt DC supply 586 is under the control of anenable signal ENAVEE, available from the video controller 113A (FIG.19).

In order to assure proper operation, the 24-volt supply 586 is connectedin a circuit as shown in FIG. 27, which includes a plurality ofcapacitors 588, 590, 592, 594; a plurality of resistors 596, 598, 600 aninductor 602; a PNP transistor 604; and a zener diode 606. The output ofthe circuitry is a nominal negative 24-volt signal LCDVEE, which isadjustable in 64 increments by way of the CONTRAST signal, as discussedabove, to vary the contrast level of the LCD display.

The keyboard controller 125 also controls the brightness of the LCDdisplay. In particular, brightness adjustment signals BRIGHTNESS₋₋ UP,BRIGHTNESS₋₋ DOWN (FIG. 15) are available at port 1, pins 6 and 7. Thesesignals BRIGHTNESS₋₋ UP and BRIGHTNESS₋₋ DOWN are normally pulled up tothe 5-volt supply 5 V₋₋ KBD by way of a pair of pull-up resistors 608and 610. These signals BRIGHTNESS₋₋ UP and BRIGHTNESS₋₋ DOWN are appliedto a digital output potentiometer 612 (FIG. 27), for example a DallasSemiconductor Model No. DS1669-50. The digital output potentiometer 612is powered by a 5-volt power supply 5 V₋₋ CORE, which is also used topull up an unused output terminal, RH.

The brightness control signals BRIGHTNESS₋₋ UP and BRIGHTNESS₋₋ DOWN areapplied to the increment and decrement terminals, UC and DC of thedigital output potentiometer 612. The output of the digital outputpotentiometer 612 is a variable resistance signal, which forms thebrightness control signal BRIGHTNESS. This brightness control signalBRIGHTNESS is pulled down by a pull-down resistor 614.

The brightness control signal BRIGHTNESS from the digital outputpotentiometer 612, as well as a backlight control signal BACKLITEON anda backlight power signal BACKLITEPOWER are connected to the system byway of a 6-pin connector 615 (FIG. 27). The backlight control signalBACKLITEON is connected to pin 4 of the connector 615 and pulled low byway of a pull-down resistor 617. The power control signal BACKLITEPOWERis applied to pins 1 and 2 while the backlight brightness control signalBRIGHTNESS is applied to pin 3. The backlight control signal BACKLITEONis available from the video controller 113A (FIG. 19) and is used topower the backlight on the LCD. The backlight power signalBACKLITEPOWER, available from an FET 619 (FIG. 20), is under the controlof the backlight power control signal BACKLITEON, available from thevideo controller 113A (FIG. 19).

The FET 619 (FIG. 20) is used to control power to both the LCD as wellas the backlight. In particular, referring to FIG. 20, the backlightpower control BACKLITEON, is used to control an NPN transistor 617 byway of a current-limiting resistor 621. The NPN transistor 621, in turn,is used to control the FET 619 to generate the backlight power signalBACKLITEPOWER at the drain terminal D1. The main power signal POWER(FIG. 28) is connected to the collector of the NPN transistor 617 by wayof a resistor 623. The main power signal POWER is also applied to asource terminal 51 of the FET 615. A gate terminal G1 of the FET 615 isconnected between the resistor 623 and the collector of the NPNtransistor 625. The backlight power control signal BACKLITEON is used toconserve power under certain power management conditions discussedabove. This signal BACKLITEON controls the NPN transistor 625. Inparticular, in a normal state, the backlight power control signalBACKLITEON is high, which turns ON the NPN transistor 625. When the NPNtransistor 625 is ON, the gate terminal G1 of the FET 619 is connectedto system ground, which turns the FET 619 ON, thereby connecting themain power signal POWER to the drain terminal D1 of the FET 619 toprovide a power signal BACKLITEIN, which is filtered by a ferrite beadinductor 625 (FIG. 28) to provide the backlight power signalBACKLITEPOWER, that is applied to the LCD by way of the connector 615(FIG. 27). When the backlight power control signal is low, for example,during a power management mode, the NPN transistor 625 turns OFF,thereby connecting the gate G1 of the FET 619 to the main power signalPOWER by way of the resistor 623, thereby turning the FET 619 OFF,disconnecting power to the LCD.

The FET 619 may be supplied as a dual element with two FETs in a singlepackage. As shown in FIG. 20, the gate G2, source S2 and drain D2terminals of the FET 619 are used to control power to the LCD, under thecontrol of an LCD enable signal ENAVDD, available from the videocontroller 113A (FIG. 19). In particular, the LCD enable signal ENAVDDis normally high and is de-asserted to disable the LCD power supplyLCD₋₋ POWER. This LCD enable signal ENAVDD is pulled low by a pull-downresistor 627 and applied to an inverter 629, whose output is connectedto the gate terminal G2 of the FET 619. The LCD power supply signalLCD₋₋ VCC (FIG. 19) is applied to the source terminal S2 of the FET 619,while the drain terminal D2 represents the LCD power signal LCD₋₋ POWER,filtered by an inductor 629 and a capacitor 631. The LCD power signalLCD₋₋ POWER is connected to the LCD by way of the connectors 732 or 734(FIG. 22). in operation, the LCD power enable signal ENAVDD is high,which turns on the FET 619 to enable the LCD power supply LCD₋₋ POWER.When the LCD power enable signal ENAVDD is de-asserted, the FET 619 isturned OFF.

The keyboard controller 125 (FIG. 15) is connected to the system databus SD [0..7]. The system address bit SA2 is used for addressing thekeyboard controller 125. In particular, the address terminal of thekeyboard controller 125 is connected to bit SA2 of the system addressbus SA[0..23].

Power to the keyboard controller 125 is provided by way of a 5-voltsupply 5 V₋₋ KBD, supplied to the power supply terminal VCC. The 5-voltsupply 5 V₋₋ KBD, provided by the DC-to-DC converter 300 (FIG. 26) byway of an in-line ferrite bead inductor 618. In addition to supplyingpower to the keyboard controller 125, the 5-volt supply 5 V₋₋ KBD isused to pull-up various pins by way of pull-up resistors 620, 622, 624,626, 628, 630, 632 and 634. In order to stabilize the 5-volt powersupply 5 V₋₋ KBD, a plurality of bypass capacitors 636 and 638 areconnected between the power supply 5 V₋₋ KBD and system ground.

As mentioned above, the keyboard controller 125 has various functions.One of those functions is to monitor when AC power is plugged into themachine from an AC adapter plug 633 (FIG. 29), connected to the externalpower supply signal AC/DCIN by way of a pair of EM1 filters 641 and 643,and a connector 645. In particular, an AC power signal ACPWR, availablefrom an FET 635 (FIG. 20), is applied to port 3, pin 1 FIG. 15) by wayof an inverter 636. The external power supply signal AC/DCIN, availablefrom the AC plug 633, is used to control the gate terminal of the FET635, normally pulled down a pull-down resistor 637. A 5-volt supply 5V₋₋ CORE is connected to the drain terminal while the source terminal isused for the AC power signal ACPWR, pulled down by a pull-down resistor639. Then an external power source is not connected to the FET 635, thesignal ACPWR will be low. Once external power is connected to theconnector 633, the signal AC/DCIN from the IBP 130 goes low, which, inturn, turns on the FET 635 to cause the signal ACPWR to go high.

The keyboard controller 125 also monitors the status of the radio. Assuch, an output from the radio TX/RX₋₋ LED pin is applied to pin 2 ofport 3 of the keyboard controller 125 by way of an inverter 638. Whenpin 1 of port 3 is high, the keyboard controller 125 interprets that theradio is in a transmit mode. Another signal from the radio CD₋₋ LED isused to provide an indication to the keyboard controller 125 that thatradio is in a receive mode. This signal CD₋₋ LED is applied to pin 2 ofport 3.

An 8 MHz clock signal 8 MHz₋₋ 5 V is used to drive the keyboardcontroller 125. The clock signal 8 MHz₋₋ 5 V is developed by the clockgenerator 398 and converted to a 5-volt level by way of the translatorsignal level translator 452.

The video controller 113A (FIG. 19) controls the video functions. Thevideo controller 113A, for example, a model number CL-GD 6205 fromCirrus Logic, can support various video modes including a mono STN and acolor TFT panel with up to 640×480 with 64 shades of gray. In addition,the video controller 113A will support 1024 by 768 resolution with 16colors on a CRT through the aid of its on-board digital to analogconverter.

The video controller 113A utilizes two clock sources for timing,generated by an internal clock generator to produce the requiredfrequencies for the display and memory timing. Two separate analog powersupply sources AVCCMCLK and AVCCVCLK are provided to the analog powersupply inputs AVCClVCLK and AVCC4MCOK on the video controller 113A.These analog power supply sources AVCCMCLK and AVCCVCLK are derived fromthe 3-volt power supply 3 V₋₋ CORE, available at the DC-to-DC converter300 (FIG. 26). In particular, the 3-volt power supply 3 V₋₋ CORE is usedto develop a 3-volt power supply VGA₋₋ VCC by way of an in-line ferritebead inductor 642. The power supply VGA₋₋ VCC, in turn, is filtered by aplurality of bypass capacitors 644-642, connected between the powersupply VGA₋₋ VCC and system ground. The 3-volt power supply VGA₋₋ VCC isused to develop the analog power supplies AVCCMCLK and AVCCVCLK by wayof a plurality of resistors 654 and 656 as well as a plurality of bypass capacitors 658 to 664, connected to an analog ground AGND. Theanalog ground AGND is tied to the digital ground GND by way of a ferritebead conductor 664.

The keyboard controller 125 also provides various miscellaneous systemfunctions by way of its I/O ports 0, 1, and 3. Five port bits P0.0-P0.5of port 0 are used for system control. Bit 0 is used to generate asignal KBC-P00, an active high signal, which disables the generalpurpose chip select signals GPCS1 and GPCS2, available at the systemcontroller 129 (FIG. 12) during boot-up, until the signals GPCS1 andGPCS2 are properly configured. As discussed above, the general purposechip select signals GPCS1 and GPCS2 are used for selecting the pencontroller 110A (FIG. 21), the radio interface 114B (FIG. 16) and theUART (134). Bit P0.1 is used to generate a contrast signal CONTRAST,normally pulled low down by a pull-down resistor 639 (FIG. 5) forcontrast control of the LCD as discussed above. Briefly, the contrastsignal CONTRAST is used to step the 24-volt supply 586 (FIG. 27). BitP0.2 is used to generate a keyboard shutdown signal KBSHUTDOWN. Thissignal KBSHUTDOWN, discussed below, is active low, and in conjunction apen shutdown signal PEN₋₋ SHUTDOWN, available at the pen controller 110A(FIG. 21), is used to generate a shutdown signal SHUTDOWN to shutdownthe AC-to-DC converter 300 (FIG. 26) during low power conditions. Moreparticularly, the keyboard shutdown signal KBSHUTDOWN, pulled up by apull-up resistor 641, and the pen shutdown signal PEN₋₋ SHUTDOWN, pulledlow by a pull-down resistor 643, are diode ORed by a pair of diodes 645and 647. The cathodes of the diodes 645 and 647 are joined to form theactive low shutdown signal SHUTDOWN. If the keyboard shutdown signalKBSHUTDOWN is asserted, the shutdown signal SHUTDOWN will be forced low,which, in turn, is used to disable the DC-to-DC converter 300 (FIG. 26).Bit P0.3 is used to generate a signal FLASHVPP to enable the flashmemory devices 742-748 (FIG. 25) to be programmed. In particular, whenthe signal FLASHVPP is low, the flash memory devices 742-748 can beprogrammed. Bit P0.4 is used to generate a signal KBC₋₋ P04. The signalKBC₋₋ P04 is an active high signal and is used to indicate to the systemcontroller 129 (FIG. 12) that a low battery condition has occurred. BitP0.5 is used for speaker control as discussed above. The pen P0.5 isused to generate the speaker disable signal SPKRDISABLE, an active highsignal.

Port 1, bits P1.1, P1.5, P1. 6, and P1.7 of the keyboard controller 125are used for system functions. Bit P1.1 is configured as an input and isused to indicate to the keyboard controller 125 that the system is in atest ode. As discussed above, the test mode signal TEST₋₋ MODE is usedto enable the flash memory device 742 (FIG. 25) to be programmed. Inparticular, as discussed above, the test mode signal TEST₋₋ MODE is usedto generate a decode signal FLIP₋₋ SA18 (FIG. 17) for decoding of theflash memory device 742. Port 1, bits P1.5, P1.6, and P1.7 are used forLCD control. In particular, the pen P1.5 may be used for LCD statuscontrol. the pens P1.6 and P1.7 are used for brightness control of theLCD as discussed above.

Port 3, bits P3.1, P3.2, P3.3, P3.4, P3.5, and P3.7 are configured asinputs. As discussed above, a signal ACPWR, available from the source ofthe FET 635 (FIG. 20), is applied to the pin P3.1. This signal ACPWRnotifies the keyboard controller 125 that an external power source isconnected to the system. The signal CD₋₋ LED is applied to the pin P3.2.This signal, CD₋₋ LED, available from the radio interface (FIG. 16),indicates that the radio is receiving a signal. A signal TX/RX₋₋ LED,also available from the radio interface, is applied to the pin P3.3.This signal TX/RX₋₋ LED indicates that the radio is in a transmit mode.A signal DOCKACK/: may be applied to the pin P3.4. This signal may beused to indicate to the keyboard controller 125 that a device is dockedto the UART 134. The development of the signal DOCKACK/: does not form apart of the present invention. A second test mode signal TEST MODE₋₋ 2may be applied to the pin P3.5 for added functions. A signal PC5₋₋ P37is applied to the pen P3.7. This signal PC5₋₋ P37 is available from thesystem controller 129 (FIG. 12) and indicates that the system is in asleep state as discussed above.

The video controller 113A is connected to the system database SD[0..15]as well as the system address bus SA[D..23] a.d is adapted to supportthe video memory 113B of either 256K by 16-bit or 256K by 4-bit videomemory chips 666 or 668. These video memory chips 666 and 668, forexample 256 K by 16 dram memory chips, as manufactured by Toshiba ModelNo. NE4244170-70, are connected to a 16-bit video memory databusVMDATA[0..15] and the 9-bit video memory address bus VMADR[0..8]. Thevideo memory chips 666 and 668 are accessed is the range fromAOOOH-BFFFFH and are switched to allow access to a full 512 kilobyterange. The video memory chips 666 and 668 are provided with dual columnaddress strobe (CAS) pins to allow byte selection. The video memorycolumn address strobes LCAS and UCAS are under the control of the highand low video memory column address strobe low and high signals, VMCASLand VMCASH, which are applied to the LCAS and UCAS pins by way of a pairof current-limiting resistors 670 and 672 to generate the buffered CASthe lower and high CAS signals VMCISLBUF and VMCASHBUF. The row addressstrobe signal VMRAS from the video controller 113A, as well as thewrite/enable signal VMWE, are also applied to the video memory 666 and668 by way of current limiting resistors 674 and 676 respectively. Theoutput/enable pin on the video memory chips 666 and 668 is under thecontrol of a video memory operate/enable signal VMOE. This video memoryoperate enable signal VMOE is generated by the video controller 113 andis applied directly to the video memory chip 666 and 668.

Various power supply signals VGA₋₋ VCC, LCD₋₋ VCC, VGABUS₋₋ VCC andVMEM₋₋ VCC are applied to the video controller 113A. The power supplyVMEM₋₋ VCC is applied to the VMEM₋₋ VCC pins on the video controller113A and is also used as the power supply for the video memory chips 666and 668. The video memory power supply VMEM₋₋ VCC may be supplied aseither a 3-volt or 5-volt power supply. More particularly, both a 3-voltand 5-volt power supply 3 V₋₋ CORE and SV₋₋ CORE. Depending on whether3-volt or 5-volt operation is selected, only one of the componentpositions illustrated as ferrite bead inductors 680 or 682 will bepopulated to produce the power supply VMEM₋₋ VCC.

As will be discussed in more detail below, the system also includes anLCD controller to control the LCD screen 113C. The power supply for theLCD controller LCD₋₋ VCC can likewise be supplied as either three voltor five volt by way of the 3- and 5-volt power supply voltages 3 V₋₋CORE and 5 V₋₋ CORE, available at the DC-to-DC converter 320 (FIG. 26).Depending on the voltage selected, only one of the component locations684 and 686 will be populated to provide the LCD power supply voltageLCD₋₋ VCC. In addition, a power supply voltage VGABUS₋₋ VCC is used forthe VGA bus. This power supply voltage VGABUS₋₋ VCC is generated by theDC-to-DC converter 320 by way of a ferrite bead inductor 688.

In order to filter noise out of the power supply signals, various bypasscapacitors are connected between the power supply signals and systemground. For example, a plurality bypass capacitors 690-696 are coupledbetween the power supply signal VMEM₋₋ VCC and the system ground.Similarly, a pair of bypass capacitors 698 and 700 are connected betweenthe power supply signal LCD₋₋ VCC and the system ground. Lastly, aplurality of bypass capacitors 702 to 706 is connected between the powersupply signal VGABUS₋₋ VCC and the system ground.

Additional filtering is provided for the analog subsystem. Inparticular, a filter consisting of a pair of capacitors 708 and 710 anda resistor 712 is connected to a filter terminal VFILTER and analogground AGND. Similarly, another pair of capacitors 714 and 716 and aresistor 718 are connected between a signal MFILTER and analog groundAGND.

The video controller 113A requires two separate clock signals: 14 MHz;and 32 KHz. The 14 MHz clock signal is used for most timing includingthe LCD panel memory and the bus cycle while the 32 KHz clock signal isused for video memory refreshing when the system is suspended. Theseclock signals are supplied by the clock generator 398 (FIG. 13) by wayof the signal level translator 452 (FIG. 14). More particularly, 32 KHzand 14 MHz clock signals 32 KHz and 14 MHz from the clock generator 398,respectively, are applied to the signal level translator 452 totransform these respective signals into 5-volt signals 32 KHz₋₋ 5 V an14 MHz₋₋ 5 V to provide a suitable clock signal voltage for the videocontroller 113A.

RGB data from the video controller 113A (FIG. 19) is supplied to the LCDscreen 113C by way of a data bus PDATA[0..17]. This data busPDATA[0..17] is applied to a plurality of current limiting resistors708-742, respectively, to generate the buffer signals PDBUF[0..17].These buffer signals PDBUF[0..17] are connected to the LCD panel 113along with various control signals by way of a pair of connectors 732and 734.

The BIOS as well as other data is stored in flash memory, for example,512 K by 8-bit memory devices 742-748 (FIG. 25). These flash memorydevices 742-748 are connected to the local ISA bus 150 by way of thesystem address bus SA[0..23] and the system data bus SD[0..15]. The chipenable pins CE of the flash memory devices 742-748 are selected by adecoder circuit (FIG. 17), as will be discussed in more detail below.The output enable pins OE on the flash memory devices 742-748 are underthe control of a memory read signal MEMR. The memory read signal MEMR isunder the control of the system controller 129. The write/enable pinsWE, which are active low, are under the control of a memory right gatesignal MEMWGATE. This signal MEMWGATE is only enabled when the flashmemory devices 742-748 are being programmed. As discussed above,programming of the flash memory devices 742-748 is under the control ofa flash program signal FLASHVPP, available at port 0.3 of the keyboardcontroller 125 (FIG. 15). This programming signal FLASHVPP, normallypulled high by a pull-up resistor 749 (FIG. 17), is ORed with a memorywrite signal MEMW by way of an OR gate 751 to generate a signal MEMGATE,an active low signal.

The power supply for the flash memory devices 742-748 is developed by a5-volt power supply signal 5 V₋₋ ROM. The 5-volt power supply signal 5V₋₋ ROM is available from the DC converter 300 (FIG. 20) by way of aferrite bead inductor 751. This power supply signal 5 V₋₋ ROM is alsoconnected to a plurality of by-pass capacitors 752-758, forstabilization.

Decoding of the flash memory devices 742-748 is provided by thecircuitry that includes the buffers 760, 762, the inverters, 764, 766,and 768 and OR 770 and a 3- to 8-bit multiplexer, Model No. 74HCT138,for example, as manufactured by Motorola and a pair of resistors 772 and774 (FIG. 17). In particular, the system address bits SA[19..21] areapplied to a 3- to 8-bit multiplexer 776. The system address bit SA18 isapplied to the inverter 760 to develop a FLIP₋₋ SA18 signal that ispulled down by the pull-down resistor 774. During a normal boot-up, theFLIP₋₋ SA18 E signal will be same as the system address bit SA18.However, during a test mode boot-up, the FLIP₋₋ SA18 signal will be lowuntil a control signal available at the control signal GPI00, availableat the system controller 129, goes low in order to enable the system toboot from the BIOS in the flash memory device 742 as will be discussedin more detail below. Once the GPI00 signal goes low, the FLIP₋₋ SA18signal will be the same as the system address bit SA18.

The multiplexer 776 is under the control of a flash memory rewritesignal MRW. This signal MRW and the system address bit SA[23]. The flashmemory read write signal MRW is under the control of an OR gate 780. TheOR gate 780, in turn, is under the control of memory read and writesignals MEMW and MER, which are applied to a pair of inverters 782 and784, respectively, and, in turn, to the OR gate 780. The memory readMEMR and memory write MEMW signals are available from the systemcontroller 129.

The output of the multiplexer 776 is used to generate the chip selectsignals CS60, CS68 and CS70. In order to provide the ability of theflash memory device 742 to be addressed during a test mode, the chipselect signal CS78 is under the control of an OR gate 770 and aplurality of inverters 764-768. During a normal mode of operation, thechip select signal CS78 will be under the control of the multiplexer776. During a normal boot up, the chip select signal CS78 for the flashmemory device 742 will be 0o under the control of a ROM chip selectsignal ROMCS, available at the system controller 129 in order to enablethe system BIOS to be shadowed into the DRAM 111A.

In order to provide the ability of the system to update the BIOS in theflash memory device 742 and to recover from a corruption of the BIOSdata in the flash memory device 742, a uniform asynchronous receivertransmitter (UART) 788 (FIG. 23) is provided. The UART 788 is connectedto the system data bus SD[0..15] and the system address bus bitsSA[0..2]. The UART 788 is powered by the 5-volt power signal 5 V₋₋ CORE,available at the DC-to-DC converter 320 (FIG. 26). A 1.84 MHz clocksignal, 1.84 MHz₋₋ 5 V, available at the signal level translator 452, isused to drive the UART 788.

A serial interface 790 (FIG. 30), consisting of a standard DB-9connector, enables external serial data to be received by the UART 788(FIG. 23). The UART signals are filtered by way of a plurality ofresistors 792-806 and bypass capacitors 802-822 and applied to anoptional disaster recovery adapter 824, an RS-232 interface, connectedto the rear of the DB-9 connector 790 and permits the flash memorydevices 742-748 (FIG. 25) to be updated by an external source in theevent of a flash disaster. The flash recovery adapter 824 may beimplemented as a DB-9 connector and is connected to the 5-volt powersupply 5 V₋₋ CORE, which, in turn, is connected to a plurality of bypasscapacitors 826 and 828. An additional four capacitors 830-836 areconnected to the module 824 as shown.

The power supply for the system includes the DC-to-DC converter 300which has the ability to provide both 3-volt and 5-volt power suppliessignals to the various subsystems as discussed. The DC-to-DC converterincludes a switching power supply 850, for example, a Maxim type 786.One source of power to the DC-to-DC converter 300 is the IBP 130, forexample, 7.2 volts nominal, as well as from an external source of ACpower connected to the plug 633 (FIG. 29).

Input power to the DC-to-DC converter 300 may be from an AC/DC converter(not shown) connected to the plug 633, which has a DC output voltagebetween 5.5-15 volts DC, applied to a power supply terminal AC/DCIN FIG.28) as well as internal batteries, for example, the IBP 130, connectedto the system by way of a connector 850 (FIG. 26). The battery supplyvoltage from the IBP 130 is connected to the battery positive terminalBATT (FIG. 28). The two supplies BATT and AC/DCIN are alternatively usedto develop a main power signal POWER (FIG. 28), that is applied to aswitching power supply 851, for example, a Maxim type 786 by way of apair of FETS 854 and 856 (IL. 26), under the control of a main powerswitch 855 (FIG. 28). The main power signal POWER is applied to a draininput D2 on each of the FETS 854 and 856. A bypass capacitor 860 isconnected to the drain terminal D2 of the FET 856 and system ground. Thesource terminals S2 of each of the FETS 854 and 856 is connected to theswitching power supply 851 to provide 5- and 3-volt references by way ofthe zener diodes 860 and 862, respectively. The gate terminals G1 and G2of the FETS 854 and 856 are under the control of the switching powersupply 851.

The switching power supply 851 provides both a 3-volt and 5-volt outputvoltages 3 V₋₋ CORE and 5 V₋₋ CORE by way of filters which include aplurality of resistors 866 and 868, a plurality of inductors 870 and872, and a plurality of capacitors 874-882 as well as a capacitor 879.For proper operation, the D1 and D2 terminals on the switching powersupply 851 are connected to the system ground along with the ground pinsPGND and GND. The SS3 and SS5 pins are connected to system ground by wayof a pair of capacitors 884 and 886.

The frequency of the switching power supply 851 is under the control ofa pair resistors 888 and 890 and a capacitor 892, connected to the SYNCand reference terminals on the switching power supply 851. A HOOK-VCCsignal is applied to the VH and VL pins of the switching power supply851. This signal HOOK-VCC is available from the module 894 (FIG. 29),discussed above. The signal HOOK-VCC signal is connected to theswitching power supply 851 by way of a resistor 896 (FIG. 26); aplurality of capacitors 898, 900 and 902; and an FET 904.

As mentioned above, both the pen controller 110A (FIG. 21) and keyboardcontroller 125 (FIG. 15) are used to develop a shutdown signal SHUTDOWN.The shutdown signal SHUTDOWN is pulled low by a pull-down resistor 906and applied to an active low shutdown pen SHDN* on the switching powersupply 851. The shutdown signal SHUTDOWN (FIG. 20) is indicative of ashutdown by the keyboard controller 125 (FIG. 15).

As mentioned above, one source of power for the system is the IBP 130which accounts for temperature and discharge rates and sends it to thekeyboard controller 125 (FIG. 15). Two predefined levels are set in theIBP 130 to indicate low battery and critical battery. The IBP 130 willinform the keyboard controller 125 of a low battery when there isapproximately five minutes left. When the battery charge is between 5minutes to 2 minutes, the IBP 130 will report a battery criticalcondition. Within the final thirty seconds the IBP 130 will force animmediate shutdown. The IBP 130 will report the battery statusapproximately once every 2.5 seconds. If the system is changing to apower savings mode, a command will be sent to the IBP 130 to put the IBP130 into a power-saving state. The IBP 130 will trl-state itscommunication lines and discontinue reporting battery status to thesystem.

A charge control signal CHGCTRL from the IBP 130 is used to controlcharging. Referring to FIG. 28, the charge control signal CHGCTRL isapplied to a zener diode 910, for example, a 5.1 V zener diode. Thezener diode 910 controls whether the IBP 130 is fast charged or tricklecharged as a function of the magnitude of the charge control signalCHGCTRL.

In particular, if the magnitude of the charge control signal CHGCRL isless than the zener breakdown voltage (i.e., less than 5.1 volts), theIBP 130 is trickle-charged by way of series pass transistor 912, a pairof resistors 914 and 916 from the external power signal POWER by way ofa diode 918, a fuse 920 and a filter consisting of an inductor 922 and acapacitor 924.

Should the charge control signal CHGCTRL be greater than the zenerbreakdown voltage of the zener diode 910, the IBP 130 will be fastcharged by way of an FET 928 whose source terminal is connected to theAC/DC converter by way of the diode 918 and drain terminal, connected tothe battery positive terminal BATT by way of the fuse 920 and theinductor 922.

The series pass transistor 912 that controls trickle charging is underthe control of an FET 930. The drain terminal of the FET 930 isconnected to the system ground while the source terminal is connected tothe base terminal of the PNP series pass transistor 912. Normally, theseries pass transistor 912 is turned off with its base terminal beinghigh by way of its connection to a pair of biasing resistors 932 and934, which, in turn, are connected to the main power signal POWER by wayof the diode 918. When the charge control signal CHGCTRL is less thanthe breakdown voltage of the zener diode 910, the charge control signalCHGCTRL turns on the FET 930 by way of the biasing resistors 936 and 938a coupling capacitor, connected to its gate terminal. Once the FET 930is turned on, it, turns on the series pass transistor 912 to provide acharging path between the main power signal POWER and the batterypositive terminal BATT.

As mentioned above, fast charging of the battery is under the control ofthe FET 928. The FET 928, in turn, is under the control of a PNPtransistor 926. The PNP transistor 926, which includes a pair of biasingresistors 940 and 942, is connected to the collector terminal of an NPNtransistor 942. The base of the NPN transistor 942 is connected to apair of biasing resistors 944 and 946 and, in turn, to a collectorterminal of another NPN transistor 948 and the main power signal POWER.The NPN transistor 948 is biased by way of a pair of biasing resistors950 and 952 and, in turn, to the anode of the zener diode 910.

In operation, when the charge control signal CHGCTRL exceeds thebreakdown voltage of the zener diode 910, the zener diode 910 conductsthereby biasing the NPN transistors 942 and 948, turning them ON. Oncethe NPN transistor 942 is turned ON, the base terminal of the PNPtransistor 926 is connected to ground, thereby turning the PNPtransistor 926 ON. The PNP transistor 926, in turn, connects the mainpower signals POWER to the gate terminal of the FET 928 by way of thediode 918, thereby turning the FET 928 ON to enable the battery positiveterminal BATT to be fast charged from the AC-to-DC converter.

As mentioned above, the wireless interface device 100 includes a radiosystem which allows for wireless interfacing with a host computer andalso wireless interfacing to both a wired local area network (LAN) and awireless LAN. The radio subsystem has been discussed above. It isimplemented by way of an interface 960 (FIG. 16), implemented by way ofa 25×2 header, which connects the radio subsystem to the balance of thecircuitry in the wireless interface device 100. In particular, thesystem data bus SD[0..15], as well as the system address bus bitsSA[0..2] are connected to the interface 960. The radio interface 960 isunder the control of the system controller 129 (FIG. 12), such as I/Owrite (IOW), I/O read (IOR) and an address enable signal (AEN)

Output signals from the radio interface 960 include the signals CD₋₋LED, TX/RX₋₋ LED, IRQ10 and IOCS16. io As discussed above, the signalCD₋₋ LED indicates a connection has been made with a host computer 101.The signal TX/RX₋₋ LED indicates that a signal is either being sent orreceived through the radio interface 960. As mentioned above theperipheral controller 128 (FIG. 13) is responsible for interruptcontrol. Thus, the radio subsystem interrupt IRQ10 is applied to theperipheral controller 128. Power supply for the radio interface 960 isby way of a 5-volt power supply signal 5 V₋₋ CORE, available at theDC-to-DC converter 300 (FIG. 26), which is filtered by a pair of bypasscapacitors 962 and 964.

The interrupts for both the radio interface 960 IRQ10, as well as theUART 788 (FIG. 23) IRQ4, are formed into a common signal IRQ10/4 andapplied to the system controller 129 by way of a resistor 966. Inparticular, the radio interface interrupt signal IRQ10 is applied to aninverter 962, whose output is ORed by way of the OR gate 964 with theUART 788 interrupt signal IRQ4. The output of the OR gate 964 forms thecombined interrupt signal IRQ10/4.

The radio interface 960, as well as the UART 788 (FIG. 23), are selectedby the chip select signals RADIOCS and URTCS. These signals areavailable at the output of a pair of the OR gates 968 and 970,respectively. The system address bit SA3 is inverted by way of aninverter 972 and ORed with a general purpose chip select gate signalGPCSlGATE by way of the OR gate 970 to generate the UART chip selectsignal UARTCS. The system address bit SA3 is applied directly to the ORgate 968 and ORed with the general purpose chip select gate signalGPCS1GATE to generate the radio chip select signal RADIOCS. The generalpurpose chip select signal gate signal GPCS1GATE is available at theoutput of an OR gate 974. In particular, a general purpose chip selectsignal GPCS1, available from the system controller 129 (FIG. 12), isORed with an output from pin 0 of port 0 of the keyboard controller 125(FIG. 15) to cause the radio interface 960 to be addressed at addressed3EO-3E7 and the UART 788 to be addressed at address 3EA-3EF. The signalKBC₋₋ P00 is normally pulled up to the 5-volt power supply voltage 5 V₋₋CORE by way of a pull-up resistor 976.

The pen controller 110A is illustrated in FIG. 21 and is adapted tocooperate with an analog-resistive type digitizer 106. The pencontroller 110A includes a controller 980, for example a Motorola typeMC68HC705J2 microcontroller, with the firmware being programmed withinthe part. The controller 980 communicates with the system by way of thesystem data bus SD[0..15]. In particular, serial data from a port PB6 onthe controller 980 is applied to a shift register 982, which, in turn,is connected to an 8-bit parallel buffer 984, which, in turn, isconnected to the serial data bus SD[0..15]. The controller 980 isadapted to be used with an analog-resistive touch screen digitizer, forexample a drawing No. 8313-34 Rev. C4, as manufactured by Dynapro. XYinformation from the digitizer 106 is received by the controller 980 byway of a connector 986. The X and Y information from the digitizer isconnected to a 12-bit analog-to-digital (A/D) converter and also appliedto port PA5 of the microcontroller 980. In particular, the X- data fromthe digitizer is applied to the A1 terminal of the A/D converter 988 byway of a pull-up resistor 990 and an FET 992. The FET 992 is under thecontrol of a charge pump 994, for example a Linear Technology Model No.LTC1157C58. The Y- data from the digitizer is applied to the terminal A1of the A/D converter 988 by way of a current-limiting resistor 994. Apair of bypass capacitors 996 and 998 are tied between the terminals A0and A1 of the A/D converter 988 and an analog ground PEN₋₋ AGND. The X+,Y+, X-, Y- inputs from the digitizer are also applied to the controllerports PA[0..4] by way of a plurality of transistors 1000, 1006, 1010,1016 and 1018; a plurality of resistors 1002, 1008, 1012, 1014, 1020,1022, 1028, 1032 and 1034; an inductor 1004; and a plurality ofcapacitors 1024 and 1026. The transistor 1018, as well as thetransistors 992 and 998, are used to prevent leakage in a suspend state.

Power from both analog and digital power supply and grounds are suppliedto the system. In particular, a 5-volt digital power supply PEN₋₋ VCC,developed from the 5-volt supply 5 V₋₋ CORE, is available from theDC-to-DC converter 300 (FIG. 26) by way of an in-line ferrite beadinductor 1028. An analog power supply PEN₋₋ AVCC is developed from thedigital supply PEN₋₋ VCC by way of an in-line ferrite bead inductor1030. The digital power supply PEN₋₋ VCC is applied to themicrocontroller 980 and filtered by a bypass capacitor 1030. The analogsupply PEN₋₋ AVC is utilized by the 12-bit analog-to-digital converter988 and filtered by way of a bypass capacitor 1032.

A separate clock supply is used for the microcontroller 980. This clocksupply includes a 4.0 MHz crystal 1034, a resistor 1036 and a pair ofparallel coupled capacitors 1038 and 1040. The clock supply is appliedto the oscillator terminals OSC1 and OSC2 of the microcontroller 980.

A 5-volt signal PENACT₋₋ 5 V, available at the port P5 V pin of themicrocontroller is converted to a 3-volt signal PENACT₋₋ 3 V by way of apair of voltage dividing resistors 1042 and 1044. This signal PENACT₋₋ 3V is applied to a 3-volt terminal of the system controller 129 (FIG.12). As discussed above, the power supply for the FETs 992 and 1018 isprovided by the charge pump 994. The power supply for the charge pump994 is a 5-volt power supply signal 5 V₋₋ CORE, available at theDC-to-DC converter 300 (FIG. 26). A ground terminal of the charge pump994 is connected to system ground by way of a pull-down resistor 1050.The 5-volt power supply PEN₋₋ VCC is also utilized by the shift register982 and the data buffer 984 and buffered by way of a pair of bypasscapacitors 985 and 987.

The chip select signal PENCS for the data buffer 984 is generated by anOR gate 1052. The general purpose chip select signal GPCS2 is availablefrom the system controller 129 (FIG. 12), as well as a signal KBC₋₋ P00,available from the keyboard controller 125 (FIG. 15) are applied to theinputs of the OR gate 1052.

A pen shut-down signal PEN₋₋ SHUTDOWN is used to develop a shut-downsignal SHUTDOWN as discussed above for turning on the switching powersupply 851 (FIG. 26). The pen shutdown signal PEN₋₋ SHUTDOWN isdeveloped by the circuit that includes the transistors 1060, 1062 and1064; a plurality of resistors 1066, 1068, 1069, 1070 and 1072; and acapacitor 1074. In particular, a 5-volt power supply signal 5 V₋₋ COREis applied to a pair of voltage-dividing resistors 1070 and 1072, which,in turn, is used to bias the transistor 1064 on. The base-emittervoltage is held fairly constant by the capacitor 1074. Once thetransistor 1064 is turned on, it is used to control the FET 1062. A mainpower supply signal POWER is applied to the gate of the FET 1062 by wayof the resistor 1069. Wake up of the system by way of the pen subsystemis discussed below.

6. Flash Disaster Recovery

As mentioned above, the wireless interface device 100 includes the flashmemory devices 742-748 (FIG. 25). As will be discussed in more detailbelow, the flash memory devices enable user software upgrades by way ofthe radio interface 960 (FIG. 16). Should power be lost during theprogramming, the data within the flash memory devices 742-748 will becorrupted, which could result in the system failing to boot.

In order to enable recovery from such a condition, recovery BIOS isstored in a protected sector of the flash memory device 742, which willbe unaffected during reprogramming. In addition, a serial port interface790 (FIG. 30) is provided to enable the flash memory devices 742-748 tobe programmed in such a condition by an alternative wired sourcefollowing a normal boot-up. Unfortunately, the configuration of theflash memory device 742 may result in the system failing to boot. Moreparticularly, disaster recovery BIOS is not stored at the uppermostaddress of the flash memory device 742. Each flash memory device 742-748are 512 K×8-bit devices. With reference to Table 5 above, the flashmemory device 742 is mapped to the address range $0C0000-$0FFFFF. Therecovery BIOS is contained in the lower half of that range (i.e.$0E0000-$0FFFF).

On a normal boot-up, the system begins executing code at the top of theaddress range (i.e. $0C0000-ODFFFF) flash memory device 742 by way ofthe system address bit SA18. More particularly, on a normal boot-up atest mode signal TEST₋₋ MODE, available at port 1.1 of the keyboardcontroller 125 (FIG. 15) is pulled high by the keyboard controller 125during boot-up, which enables the buffer 762 (FIG. 17) which, in turn,enables another buffer 760 to enable the system address bit SA18 duringboot-up. When the system address bit SA18 is enabled, the system beginsexecuting code at the top of the address range ($0C0000) of the flashmemory device 742. However, during a condition when the data in the tophalf of the address range ($0C00000-0DFFFFF) becomes corrupt as a resultof a problem occurring during reprogramming, the system may not bootduring such a condition.

In order to solve this problem, the system address bit SA18 is forcedlow. By forcing the system address bit SA18 low, the system will beginexecuting code from the protected area of the flash device 742 in theaddress range ($0E0000-$0FFFF) during such a condition where thedisaster recovery BIOS resides in a protected sector. In particular, thesystem address bit SA18 is applied to the buffer 760 (FIG. 17), which isunder the control of the test mode signal TEST₋₋ MODE by way of thebuffer 762. The output of the buffer 760 is a signal FLIP₋₋ SA18, whichis applied to the address pin A18 (FIG. 25) on the flash memory device742.

During a normal boot-up, the test mode signal TEST₋₋ MODE will enablethe buffer 762 (FIG. 17) and, in turn, the buffer 760 to cause thesystem address bit SA18 to drive the signal FLIP₋₋ SA18. During acondition when the code in the flash memory device 742 becomes corrupt,the test mode signal TEST₋₋ MODE is forced low, which, in turn, forcesthe signal FLIP₋₋ SA18 low, resulting in the system executing code fromthe protected area (i.e. $0E0000-0FFFF) of the flash memory device 742during such a condition to enable the flash memory device 742 (FIG. 25)to be reprogrammed by way of the serial interface 790 (FIG. 30).

There are various ways in which to force the test mode signal TEST₋₋MODE low during reprogramming of the flash memory device 742 by way ofthe serial interface 790. One way is to externally ground the test modesignal TEST₋₋ MODE during such a condition. In particular, the test modesignal TEST₋₋ MODE may be connected to one pin of a two-pin header 1100(FIG. 30). The other pin of the header 1100 is connected to systemground. During reprogramming of the flash memory device 742, an externaljumper (not shown) is inserted into the header 1100 to shunt the testmode signal TEST₋₋ MODE to system ground to enable the system to executecode from the protected or boot block area of the flash memory device742 in order to enable the system to be booted. Once the system isbooted, the flash memory device 742 is reprogrammed by way of the serialinterface 894 (FIG. 29). Once reprogramming is complete, the shunt isremoved from the header 1100 (FIG. 30) and the adapter plug 790 isremoved, restoring the system to normal operation.

7. Resume on Pen Contact

In order to conserve battery power, the wireless interface device 100goes into a suspend mode when the system is not in use. As discussedabove, a shut down signal SHUTDOWN (FIGS. 20 and 26) is used to shutdown the power supply 851 (FIG. 26) during such a condition, whichessentially disables the power to all but the circuitry required todetect a pen down event by way of the main power signal POWER (FIG. 28).

Three sources control the shut down signal SHUTDOWN: the keyboardcontroller 125 (FIG. 15); the pen controller 110A (FIG. 21) and a signalHOOK₋₋ VCC, connected to the switching power supply 851 (FIG. 26) by wayof the FET 904. These sources are diode ORed to the shut down signalSHUTDOWN by way of the diodes 645 and 647 (FIG. 20) and a diode 1102(FIG. 28). During a normal state, the shut down signal SHUTDOWN is high,which enables the power supply 851 (FIG. 26). When the shut down signalSHUTDOWN goes low, the power supply 851 goes into an inactive state.During the inactive state, minimum power is supplied to the pendetection circuitry as discussed above.

As will be discussed in more detail below, once the system is turned onby the main power switch 855 (FIG. 28), the shut down signal SHUTDOWNwill be under the control of the pen shutdown signal PEN₋₋ SHUTDOWN,available from the pen controller 110A (FIG. 21) and the keyboardcontroller shut down signal KBSHUTDOWN (FIG. 20).

The keyboard controller 125 (FIG. 15) can place the system in a suspendstate by way of a command, which, in turn, causes the keyboardcontroller shut down signal KBSHUTDOWN, available at port P0.2, to golow. More particularly, during normal operation, only the keyboardshutdown signal KBSHUTDOWN is high, placing control of the suspend statesolely in the keyboard controller 125. The keyboard controller 125 canthen force the system into a suspend state by forcing port P0.2 low,which, in turn, places the power supply 851 (FIG. 26) in an inactivestate.

The pen shut down control signal PEN₋₋ SHUTDOWN is used to wake thesystem from a suspend state. More particularly, as mentioned above,during a suspend state, power from the main power supply POWER (FIG. 28)is applied to the collector of the transistor 1064 (FIG. 21) and to thedrain of the FET 1062. Since the 5-volt power supply 5 V₋₋ CORE isunavailable during a suspend state, the transistor 1064 will be OFF,allowing power to appear at the gate of the FET 1062, thus turning theFET 1062 ON. Once the FET 1062 is turned ON, the main power signal POWERis applied to the XPLUS terminal of the digitizer panel. Thus, a pen (orfinger) down event will result in the YPLUS terminal being connected tothe XPLUS terminal by way of a finite resistance (ire. 500-1500 Ohms) toapply power to the YPLUS terminal, which, in turn, is connected to thedrain of the P-channel FET 1060 while its source is used as the penshutdown signal PEN₋₋ SHUTDOWN. The FET 1060 is under the control of aleakage signal LEAKAGE, available at the output of the charge pump 994.Since the leakage signal LEAKAGE will be low during a suspend state, theFET 1060 will turn on in response to the pen down event, therebyconnecting the YPLUS terminal to the pen shut down signal PEN₋₋SHUTDOWN. As mentioned above, the YPLUS terminal will be high inresponse to a pen down event following a suspend state. As such, the penshut down signal PEN₋₋ SHUTDOWN will go high. Since the pen shut downsignal PEN₋₋ SHUTDOWN is diode ORed with the shut down signal SHUTDOWN,the shut down signal SHUTDOWN will thus be forced high in response to apen down event following a suspend state, which, in turn, will wake upthe power supply 851 (FIG. 26). Once the system is wakened, the keyboardcontroller shutdown line KB₋₋ SHUTDOWN goes high, latching the systemON. The resistors 1070, 1072 and the capacitor 1074 are used to delayturning ON the transistor 1064 and the turning OFF of the FET 1062before the keyboard shutdown signal KB₋₋ SHUTDOWN is pulled high whichwould cause the pen shut down signal PEN₋₋ SHUTDOWN to go low before thekeyboard shutdown signal KB₋₋ SHUTDOWN goes high.

The FETs 992, 998 and 1018 are used to prevent current leakage in asuspend state. In particular, these FETs 992, 998 and 1018 are under thecontrol of the leakage control signal LEAKAGE, available at the chargepump 994, which turns the FETs 992, 998 and 1018 ON in normal operateand OFF in a suspend state.

The sensing of suspend state is done by the charge pump 994, whichmonitors the 5-volt power supply signal 5 V₋₋ CORE. When the 5-voltpower supply signal 5 V₋₋ CORE goes low, indicating a suspend state, theleakage control signal LEAKAGE goes high, turning off the FETs 992, 998and 1018, blocking leakage into the pen circuitry from the XPLUSterminal.

8. RC Time Constant

The system ON/OFF switch 855 (FIG. 28) enables the system to becompletely shut off. When the switch 855 is closed, power from eitherthe IBP 130 or the external AC-to-DC converter supplies power to thesystem. In order to wake up the system from an OFF state, a shutdownline SHUTDOWN must be held high until the keyboard controller 125 pullsits shutdown pin KB₋₋ SHUTDOWN high. As discussed above, the keyboardshutdown signal KB₋₋ SHUTDOWN is diode ORed relative to the shutdownsignal SHUTDOWN, which controls the power supply 851 (FIG. 26). Untilthe time when the keyboard shutdown signal KB₋₋ SHUTDOWN is pulled high,a signal HOOK₋₋ VCC is used to force the shut down signal SHUTDOWN high.As mentioned above, the HOOK₋₋ VCC signal is also diode ORed relative tothe shutdown signal SHUTDOWN by way of the diode 1102 (FIG. 28).However, for proper operation of the system, the shutdown signalSHUTDOWN will be under the control of the keyboard controller 125 (FIG.15) after the system is turned on Thus, a 5-volt power supply signalHOOK₋₋ VCC, available at the power supply 851 (FIG. 26), forces the shutdown signal SHUTDOWN high until the keyboard controller 125 (FIG. 15)has time to pull its keyboard shutdown signal KB₋₋ SHUTDOWN high. The5-volt power supply signal HOOK₋₋ VCC is always high when the main powerswitch 855 is turned on. On power-up, the 5-volt power supply signalHOOK₋₋ VCC forces the shutdown signal SHUTDOWN (FIG. 28) high by way ofan FET 1104 and the diode 1102, which, in turn, wakes up the powersupply 851 (FIG. 26). Once the power supply 851 is enabled, a powersupply signal MAX 786₋₋ VCC is used to turn off the FET 1104 to placethe control of the shut down signal SHUTDOWN under the control of thekeyboard controller 125 as discussed above. In order to providesufficient time for the keyboard controller 125 to pull its keyboardshutdown signal KB₋₋ SHUTDOWN high, the turn OFF of the FET 1104 isdelayed by way of a resistor 1106 and a capacitor 1108. In particular,once the main power switch 855 is closed, the power supply signalMAX786₋₋ VCC will be low, thereby causing the FET 1104 to be turned ON,which connects the power supply signal HOOK₋₋ VCC to the shutdown signalSHUTDOWN by way of the diode 1107. Once the power supply 851 is enabled,the signal MAX786₋₋ VCC, applied to the gate of the FET 1104, turns offthe FET 1104, placing the shutdown signal SHUTDOWN under the control ofthe keyboard controller shutdown signal KB₋₋ SHUTDOWN as discussedabove. The resistor 1106 and capacitor 1108 delay the turning off of theFET 1104 after the signal MAX786₋₋ VCC goes high for a sufficient timeto allow the keyboard controller 125 to pull its keyboard shut downsignal KB₋₋ SHUTDOWN high.

An inhibit circuit (FIG. 26), which includes a plurality of resistors1110-1120, a diode 1122, a transistor 1124 and an FET 1126, is used toprevent the system from being turned ON during low battery conditionswhen the system is being supplied solely by the IBP 130. During a normalcondition (i.e, when the system is being supplied power by the AC/DCconverter or by the battery, the signal MAX786₋₋ VCC is connected to themain power signal POWER by way of the FET 1126. The FET 1126 is underthe control of the transistor 1124. During conditions when the AC/DCconverter is supplying power to the system, a signal AC/DCIN will behigh, thereby turning ON the transistor 1124, which, in turn, turns ONthe PET 1126, connecting the main power signal POWER to the signalMAX786₋₋ VCC. The collector of the transistor 1124, in turn, controlsthe FET 904, which connects the power supply signal HOOK₋₋ VCC to theenable terminals ON3 and ON5 on the power supply 851. When AC power isnot available, the AC/DCIN goes low, leaving the control of thetransistor 1124 under the control of an inhibit signal INHIBIT,available from the IBP 130 by way of the connector 850. During a normalbattery condition, the inhibit signal is high, keeping the transistor1124 turned ON, thereby enabling the power supply 851 by way of the FET904. Should a low battery condition occur, the inhibit signal goes low,turning OFF the transistors 904, 1124, as well as the FET 1126, toprevent the system from being turned ON.

9. Mouse Emulation with Passive Pen

As mentioned above, the wireless interface device 100 includes adigitizer 110B and utilizes a passive pen as an input device. FIGS.31-35 illustrate a method for emulating the functions of a mouse, forexample a two-button mouse, to provide standard mouse functions with thepassive pen.

There are three aspects of the mouse emulation. One aspect relates toemulation of a double click of a mouse button, required by someapplication programs.

Another aspect relates to emulating both the left and right buttons of atwo-button mouse. The third aspect relates to emulating both themovement of the mouse (MOVE MODE) and the clicking of a mouse button(TOUCH MODE) with a passive pen as an input device.

Referring first to FIG. 31, the mouse emulation system is event-drivenby the passive pen. Initially the system checks to see if the passiveDen has touched anywhere on the LCD 113C (FIG. 36), which includes adisplay area 1200 and a hot icon area 1202. If a pen-down event has beendetected, the system checks in step 1204 if the wireless interfacedevice 100 has been placed in a calibration mode. If so, a calibrationhandler is called in step 1206. The calibration handler does not formpart of the present invention. If the wireless interface device 100 isnot in the calibration mode, the system then checks to determine if thepen has been lifted from the LCD 113C in step 1208. If a pen-up eventoccurs subsequent to a pen-down event, control is passed to a hot iconidentification (ID) processor (FIG. 32) in step 1210, which, as will bediscussed below, processes the pen position to determine which of thehot icons in the hot icon area 1202 of the LCD screen 113C was selected.If the pen was not lifted from the LCD 113C, the system checks in step1212 if the previous event in a previous cycle was a pen-up event. Ifthe previous pen event in the previous cycle was a pen-down event, thecurrent pen event is processed by a mouse mode handler (FIG. 33) in step1214, which, as will be discussed in more detail below, determines ifthe pen is being used in a mouse MOVE or mouse TOUCH MODE. In step 1216,the coordinates of the current pen-down event are processed to determineif the current pen-down event occurred in the hot icon area 1202 of theLCD 113C. If the pen-down event occurred in the hot icon area 1202 (FIG.36), a flag is turned on indicating the hot icon area 1202 was selectedin step 1218. If the system determines the current pen-down eventoccurred in the display area 1200 (FIG. 36) of the LCD screen 113C, anaudio click is generated in step 1220; different from the hot icon audioclick.

Steps 1204-1220 are driven by each pen event in order to determine thelocation of the pen-down event (i.e. hot icon area 1202 or display area1200). Once the system determines where the pen event occurred, the pendata is converted to mouse data in step 1222 and a cursor is displayedin the viewing area 1200, corresponding to the location of the pen touchin step 1224. After the cursor is displayed, the system determines instep 1226 whether the mouse data is to be used locally by the wirelessinterface device 100 for local applications or the application runningon the host computer 101. As mentioned above, the wireless interfacedevice 100, through its graphical user interface, provides a virtual oron-screen keyboard (OSK). Thus, if the OSK has been activated and thepen event occurs in the OSK area, the mouse data is used locally by thewireless interface device 100 in step 1228. If the wireless interfacedevice 100 is running a host application, the mouse data is sent to thehost computer 101 application over the wireless interface as discussedabove in step 1230

As mentioned above, the system is able to emulate both left and rightmouse buttons. This emulation is accomplished by way of left/right mousebutton hot icon 1232 (FIG. 37). A left mouse button is configured to bethe default setting. This hot icon 1232 is set up as a toggle. Thus,when the system is first turned on, the pen events from the mouse modehandler are translated to be left mouse button events. Anytime theleft/right mouse button hot icon 1232 is selected, the system willtoggle and translate subsequent pen events to be right mouse buttonevents. A subsequent pen-down event on the hot icon 1232 causessubsequent pen events from the mouse mode handler to be translated asleft mouse button events and so on.

The hot icons in the hot icon area 1202 (FIG. 36) are triggered by apen-down event followed by a pen-up event. As discussed above, such asequence of pen events is processed by hot icon ID processor 1210,illustrated in FIG. 32. The hot icon ID processor 1210 first determinesif the pen event occurred in the viewing area 1200 (FIG. 36) of the LCD113C by determining from the mouse mode handler 1214 (FIG. 33) whetherthe system is in the TOUCH in step 1234, since this mode only occurs forpen events in the viewing area 1200 of the LCD display 113C. If thesystem is not in a TOUCH mode, the system checks in step 1236 whetherthe system is in the MOVE mode. If the pen event (i.e. pen-down followedby a pen-up event) did not occur in the viewing area 1200 of the LCDdisplay 113C, the system compares the coordinates of the pen-down eventwith the locations of the various hot icons displayed in FIG. 37 in step1238. In step 1240 (FIG. 32), the system determines if the left/rightmouse button hot icon 1232 was selected. If not, the system proceedsdirectly to step 1242 to uplevel software for processing. If the systemdetermines that the left/right mouse hot icon 1232 was selected, thesystem emulates a left or right mouse button in step 1244, depending onthe last status of the left/right mouse button emulation and utilizesthe emulated left or right mouse button status in the uplevel softwarein step 1242.

Pen events in the hot icon area 1202 of the LCD display 113C are handledby the hot icon ID processor 1210 (FIG. 32), while pen events in theviewing area 1200 are handled by the mouse mode handler 1214 (FIG. 33).The mouse mode handler 1214 emulates two mouse actions: moving withouteither button being depressed and released (MOVE); and button depressionand release events (TOUCH). As discussed above, both left and rightmouse button events can be emulated in the TOUCH.

As discussed above, a current pen-down event preceded by a pen-downevent activates the mouse mode handler 1214 (FIG. 33). In step 1246, thesystem first determines if the hot icon flag is on. As discussed above,the hot icon flag is turned on anytime a pen-down event occurs in thehot icon area 1202 (FIG. 36) of the LCD display 113C. If the hot iconflag is not on, the pen-down event is translated to a mouse button downevent by a mouse TOUCH handler in step 1248. If the hot icon flag is on,the system determines in step 1250 whether the coordinates of thecurrent pen-down event to determine if the current pen-down eventoccurred in the hot icon area 1202. If so, the pen coordinate data isdropped in step 1252 since such data will be processed by the hot iconID processor 1210 (FIG. 32) discussed above. If the current pen eventoccurred in the viewing area 1200, the pen coordinate data is translatedto mouse move data.

A mouse button double click is emulated by two pen-down events separatedby a pen-up event in the viewing area 1200 of the LCD 113C. Inparticular, when the host computer 101 is running a Windows application,a pen driver translates the two pen-down events separated by a pen-upevent and passes four mouse messages: mouse button down; mouse buttonrelease, mouse button down and mouse button release to the host Windowsapplication.

As will be discussed in more detail below, the host manager Windowsmodule 1260 modifies a Windows configuration file. (WIN.INI) and, inparticular, the distance and time limitations for a mouse button doubleclick. In particular, the Windows system checks the Windowsconfiguration file WIN.INI in order to compare the distance between themouse locations for each of the clicks as well as the time betweenclicks. More particularly, the Windows systems will only pass doubleclick data to a Windows application program if the distance (i.e. heightand width) between mouse locations for the two clicks is less than 16for both height and width and the time between the clicks is less than1.0 seconds.

With a pen-based system two pen-down events separated by a pen-up eventnormally take longer and occur at greater distances between pen-downevents than allowed by the Windows system to generate a double click.Thus, the host manager Windows module 1260 modifies the time anddistance parameters to enable two pen-down events separated by a pen-upevent to enable Windows to emulate a mouse double click that can bepassed on to the Windows application program running in the hostcomputer 101. In particular, the host manager Windows module 1260includes is an initializer 1262 which loads the host manager Windowsmodule 1260, and an initial icon displayer 1264, which displays that thehost manager Windows module 1264 has been loaded. The host managerWindows module 1260 also includes a double click configuration modifier1266. The double click configuration modifier 1266 modifies theconfiguration of the Windows systems file WIN.INI by modifying the timeor speed in step 1268. The distance, broken down into width and length,between the successive pen-down events, is modified by a double clickwidth modifier and a double click height modifier in steps 1270 and1272. The modified speed, width and height parameters are set in theWindows system file WIN.INI running in the host computer 101 in step1274 to enable a mouse button double click to be emulated by twosuccessive pen-down events.

Normally, the Window system file WIN.INI is in cache. The host managerWindows manager disables the in cache copy of the Windows system fileWIN.INI, which allows the Windows system to go to the modifiedconfiguration file with the modified parameters.

10. Disable Screen Saver to Reduce LAN Traffic

As mentioned above, the wireless interface device 100 connects to a hostcomputer 101 and displays whatever is being displayed on the hostcomputer 101. In particular, after a connection is made, all of thescreen images on the host computer 101 are passed on to the LCD display113C on the wireless interface device 100. Whenever the host computer101 is running a screen saver, the host display will continually change,passing on all of the images to the LCD 113C on the wireless interface100, which creates a lot of unnecessary traffic on the LAN. In order toreduce this unnecessary LAN traffic, a host manager Windows module 1278(FIG. 39) disables the screen saver on the host computer 101 anytime aconnection is made between the host computer 101 and the wirelessinterface device 100. Anytime the connection between the host computer101 and the wireless interface device 100 is broken, the host managerWindows module re-enables the screen saver on the host computer 101.

The connection status between the host computer 101 and the wirelessinterface device 100 is under the control of a host manager DOS module1280 (FIG. 38), a terminate and stay resident program. The host managerDOS module 1280 is driven by a timer tick interrupt and checks theconnection status at each timer tick interrupt. If the connection statushas changed, the host manager DOS module 1280 calls a host managercommunicator 1282, which passes the new status to the host managerWindows module 1278.

Referring to FIG. 39, anytime the connection status between the hostcomputer 101 and the wireless interface device 100 changes, the hostmanager Windows module 1278 checks the new status in step 1284. If theconnection has been lost, a screen saver disable module 1286 is called,which, in turn, calls several Windows modules: Windows SoftwareDevelopment kit functions; SystemParametersInfo; andWritePrivateProfileString to disable the screen saver. Should thecurrent status indicate that the wireless interface device 100 isconnected to the host computer 101, the system proceeds to step 1288,which calls the various Windows module.

Referring to FIG. 40, anytime the host manager DOS module 1280 isloaded, an initial connection status checker 1290 calls the host managerDOS module 1280 to obtain the current connection status between thewireless interface device 100 and the host computer 101. Next, thesystem checks in step 1292 whether a connection exists between the hostcomputer 101 and the wireless interface device 100. If not, the systemreturns. If there is a connection, a virtual key poster 1294 posts avirtual key V₋₋ TAB into the Windows Systems queue to force the Windowsprogram to disable the current active screen saver automatically, which,in essence, simulates the press of a key on a keyboard. Once the currentactive screen saver is disabled, the screen saver on/off flag in aWindows configuration file is turned off in step 1296 to disable thescreen saver until there is a change in the connection status.

11. Host Access Protection Password

Whenever a connection is made between wireless interface device 100 andthe host computer 101, the user can optionally blank the screen on thehost computer 101 and disable the keyboard and mouse inputs connected tothe host computer 101. These features prevent the host computer 101 frombeing accessed while the host computer 101 is under the control of thewireless interface device 100 at a remote location. Once the connectionbetween the host computer 101 and the wireless interface device 100 islost, the keyboard and mouse inputs on the host computer 101 are reenabled under the control of the host manager program residing in thehost computer 101.

There are certain situations where the screen to the host computer 101may not be enabled on disconnection, for example, when the disconnectionoccurs because the wireless interface device 100 is either out of poweror out of range. In order to enable the user to access the host computer101 in such a situation, a host manager 1300 (FIG. 40A) first checkswhether the connection status has changed in step 1302 in the manner asdiscussed above. If the system is connected, no action is required.However, if the connection has been broken, the system checks in step1304 whether the screen is enabled. If not, the user will have normalaccess to the host computer 101. If so, the latest log-in password bythe user is stored in by the system in step 1306 Since the host managerDOS module controls the screen, the system checks in step 1308 todetermine whether Windows is running in the host computer 101. If DOS isrunning, the system compares the password entered on the keyboard withthe latest log-in password in steps 1310 and 1312. If the passwordentered does not match the correct password, the system returns to step1310 and awaits another keyboard input. If the correct password entered,the screen is turned on in step 1314.

Should the host computer 101 be running Windows, as determined in step1308, the latest log-in password is passed to a host manager Windowsmodule in step 1316. The system next checks in steps 1318 and 1320whether the correct password was entered in a similar manner asdiscussed above. If so, since DOS handles the enabling of the screen onthe host computer 101, the host manager DOS module is notified that thecorrect password was entered in step 1322, which, in turn, enables thescreen in step 1314.

12. Double Pen-Up Events

The pen controller 110A (FIG. 21) normally generates a series ofinterrupts and, in turn, a series of pen packets whenever the pentouches the LCD 113C (a pen-down event) and is lifted from the LCD 113C(a pen-up event) and generates an interrupt. For each interrupt, asingle packet is generated. The format of the possible packets isillustrated in Table 7 below, where x0 is bit 0 of the x coordinate ofthe pen location and y0 is bit 0 of the y coordinate of the penlocation, etc.

                  TABLE 7                                                         ______________________________________                                        PACKET BIT     BIT    BIT  BIT  BIT   BIT  BIT  BIT                             NAME 7 6 5 4 3 2 1 0                                                        ______________________________________                                        P1     1       1      0    x11  x10   x9   x8   x7                              P2 0 x6 x5 x4 x3 x2 x1 x0                                                     P3 0 0 0 y11 y10 y9 y8 y7                                                     P4 0 y6 y5 y4 y3 y2 y1 y0                                                     P5 1 0 0 0 0 0 0 0                                                          ______________________________________                                    

The packets are generated in the following sequence (p1, p2, p3, p4),(p1, p2, p3, p4). . . (p1, p2, p3, p4), (p5). The packets p1, p2, p3, p4relate to pen-down events (a pen point); each group of packets (p1, p3,p3, p4) relating to one x-y coordinate of the pen. The packet p5 relatesto a pen-up event. Thus, anytime the pen is lifted from the digitizer,one packet p5 is generated. Thus, when the pen first touches thedigitizer panel and is moved across the digitizer, a plurality of penpoints (p1, p2, p3, p4) are generated which correspond to the x, ylocations of the points touched by the pen. Normally 110 pen points persecond are generated by the pen controller 110A.

Whenever a 12-bit serial pen packet is generated by the pen controller110A and read by a firmware module in step 1330 (FIG. 41), an interruptis generated in step 1332. A pen packet assembler assembles the packetsinto pen points (p1, p2, p3, p4). These pen points (p1, p2, p3, p4) areprocessed and passed to the applications program. In order to processeach pen point (p1, p2, p3, p4), the interrupts must be disabled. Duringthe time when the interrupts are disabled, the pen point packets (p1,p2, p3, p4) and the pen-up packets p5 are generated by the pencontroller 111A but not processed and thus are garbled or lost. Lost orgarbled pen point packets (p1, p2, p3, p4) do not affect mouseemulation. However, since mouse emulation is based on both pen-down andpen-up events, lost pen-up packets p5 can result in the mouse emulationbeing hampered, possibly resulting in the system being stuck in thestate preceding the pen-up event.

In order to solve this problem, a firmware module 1330 generates twopen-up packets p5. More particularly, with reference to FIG. 42, thefirmware module 1330 reads in the 12-bit serial data from the pencontroller 110A into packets in step 1334. Next, the system checks instep 1336 whether the packet was a pen-up packet p5. If not, the systemproceeds to the pen driver in step 1332 (FIG. 41). If the packet is apen-up packet p5, the system checks to determine if the pen-up packet p5is the first pen-up packet in step 1338. If not, the system passes thepacket to the pen driver in step 1332 as discussed above. If the systemdetermines in step 1338 that the pen-up packet p5 is the first pen-uppacket p5, the serial data for second pen-up packet p5 is generated instep 1340 and assembled in step 1334. In addition, the first pen-uppacket p5 is passed to the pen driver.

The pen driver 1332 (FIG. 43) is responsive to an interrupt that isgenerated each time a packet is assembled. In response to an interrupt,the pen driver reads the packet in step 1342. In step 1344, the pendriver determines whether the packet is a pen-up packet p5. If not, thepen packet assembler processes the packet in step 1346. If the systemdetermines in step 1344 that the packet is a pen-up packet, it nextchecks in step 1346 whether the packet is the second pen-up packet. Ifso, indicating that the first pen-up packet was processed, the secondpen-up packet is dropped in step 1348. If not, the packet is determinedto be a first pen packet, which is processed by the pen packet assemblerin step 1346.

13. Seamless Integration of Wired and Wireless LANS

The wireless interface device 100 may be connected to host computer 101by way of a wireless LAN. The wireless LAN protocol is Novell open datalink interface IPXODI protocol. Since the IPXODI protocol is also usedfor wired LAN's, it would be desirable to connect the wireless interfacedevice 100 to a wired LAN system and utilize the Novell IPXODI protocol.Unfortunately, the IPXODI protocol can only communicate with a singleLAN card at a time, either a wired LAN card or a wireless LAN card atone time.

The standard Novell LAN stack conf iguration is illustrated in FIG. 45.The LAN card is identified with the reference numeral 1352.Communication between the LAN card 1352 and the IPXODI protocol is byway of a driver 1354. The driver 1354 communicates with the IPXODIprotocol (IPXODI.COM) 1355 by way of a link support layer LSL.COM 1356.The Novell IPXODI protocol passes data between the applications programs1358 and the link support layer LSL.COM 1356. Even though the linksupport layer LSL.COM can support multiple LAN cards, the IPXODIprotocol only supports a single LAN card.

In order to enable the Novell IPXODI protocol to support a configurationas illustrated in FIG. 44 to enable the wireless interface device 100 toconnect to both a wired LAN card 1352 and a wireless LAN card 1360, anadditional layer IPXMUX.COM (FIG. 46) is provided for multiplexingincoming and outgoing packets to and from the wired LAN card 1352 andthe wireless LAN card 1360. The multiplexer IPXMUX.COM manipulates thedata packet source and destination addresses to simulate a single LANcard so as to be compatible with the IPXODI protocol. By providing theadditional layer IPXMUX.COM, the host computer 101, as well as thewireless interface device 100, will be able to access all of the LANresources 1350 (FIG. 44).

Referring to FIG. 46, the additional layer IPXMUX.COM is stacked betweenthe Novell IPXODI protocol IPXODI.COM 1355 and the link support layerLSL.COM 1356. As mentioned above, the link support layer LSL.COM 1356can support two LAN cards. Thus, a wireless LAN card 1360 and acorresponding wireless LAN card driver 1362, which communicates with thelink support layer LSL.COM 1356 along with the wired LAN card 1352 andits corresponding driver 1354, can communicate with IPXODI.COM by way ofthe driver.

The multiplexer IPXMUX.COM 1364 multiplexes or interleaves the data fromboth the wireless LAN card driver 1354 and the wired LAN card driver1362 to the IPXODI protocol by manipulating the source and destinationaddresses of incoming and outgoing packets, so that as far as the NovellIPXODI protocol is concerned, it is only communicating with a single LANcard. Similarly, communication from the host computer 101, as well asapplications 1358, which may be running on the wireless interface device100, to both the wired LAN card 1352 and the wireless LAN card isformatted by the IPXODI.COM and multiplexed to either the wireless LANcard 1360 or wired LAN card 1352 by the multiplexer IPXMUX.COM by way ofthe link support layer. The multiplexer IPYMUX.COM 1364 is loaded afterthe wired LAN card driver 1354 and the wireless LAN card driver 1362 areloaded and before IPXODI.COM 1355.

The Novell LAN software includes a configuration file which checks theparticular LAN cards 1352 being run by the LAN card driver 1354. Thesystem is initialized by the routine illustrated in FIG. 47, which isrun each time the multiplexer IPXMUX.COM 1364 is loaded. Initially, acommand line parser 1366 is used to determine whether the user hasissued commands to either load or unload IPXMUX.COM command in step1368. If the command is an unload command, the system checks whetherIPXMUX.COM 1364 has already been loaded in step 1370. If so, the systemunloads IPXMUX.COM 1364 in step 1372. If IPXMUX.COM 1364 has not beenloaded, the system exits the initialization routine.

If the command was to load IPXMUX, the system checks in step 1374 todetermine if the link support layer LSL.COM 1356 has been loaded. Ifnot, the system exits the initialization routine since IPXMUX.COM cannotbe loaded until the link support layer LSL.COM has been loaded If thelink support layer LSL.COM 1356 was loaded, control is passed to a LANconfiguration browser in step 1376 to browse the LAN configuration forthe number of LAN cards and the frame types of the cards and the numberof frame types (i.e. IEEE 802.2, 802.3, etc.) to find out which LAN carddrivers are running. In addition, the browser finds and saves allrelevant application program interface entry points to the link supportlayer LSL.COM and sets to those supported by IPXMUX. COM. The browseralso sets the LSL interrupt vector to the interrupt vector supported byIPXMUX.COM, as well as finds and saves all logical board numbers.

In order to interleave the data from the wired LAN card 1352 (FIG. 46)and the wireless LAN card 1360 to IPXODI.COM to emulate a single LANcard, 2F interrupt calls from the application program by way ofIPXODI.COM are trapped and handled by a separate routine. In particular,2F interrupt calls are checked in step 1378 to determine if such callsare interrupt calls to LSL.COM. If not, the system exits. If so, theaddress of the LSL protocol support API handler supported by IPXMUX.COMis returned. Interrupt calls to LSL.COM from an application program arehandled by a special interrupt handler. If the interrupt call is toLSL.COM, a LSL initialization entry point, supported by IPXMUX.COM isreturned in step 1380. The LSL initialization entry point represents anaddress of the protocol initialization routine into LSL.COM.

Once the address of the LSL initialization entry point is known by theIPXODI protocol, the IPXODI protocol will call that address for service.Thus, all LSL service calls are checked in step 1382 (FIG. 49) todetermine if the call is a request for protocol support API entry point.If not, the multiplexer IPXMUX.COM will direct that call into LSL.COM.If so, an address of a special 2F interrupt handler (LSL ProtocolSupport API Handler) supported by IPXMUX.COM is returned to IPXODI.COMin step 1384.

The special interrupt handler, LSL Protocol Support API Handler, whichforms a part of IPXMUX.COM, is illustrated in FIG. 50. Three servicesare handled by the LSL Protocol Support Handler, which is supported bythe multiplexer IPXMUX.COM to set up an address for communication with ahost on the network. These services are register protocol stack, bindstack and send a packet. The balance of the services are handled byLSL.COM.

The entry point of the LSL Protocol Support API Handler in IPMMUX.COMfrom the standpoint of IPXODI.COM is the protocol support API within thelink support layer LSL. Since the link support layer LSL.COM supportsvarious protocols, such as IPXODI and TCPIP, registration of theIPXODI.COM protocol is checked in step 1386. If the call to the linksupport layer LSL is to register a protocol stack, an IPXMUX registerprotocol stack application program interface (API) handler in step 1388checks whether the protocol stack is IPXODI. If the protocol stack isIPXODI, the protocol stack handler sets a packet receive handler,supported by IPXMUX.COM and calls LSL.COM's protocol stick API toregister the protocol. The protocol stack handler also saves the stackID. Subsequently, in step 1390, an IPXMUX Receive Routine Linker setsthe protocol stack IPXODI's receive routine address to the packetreceive address supported by IPXMUX.COM.

If the protocol API call is not to register the protocol stack, thesystem then checks in step 1392 whether a special registration service,a bind stack service, is requested. A bind stack service, normally donebefore registration, is used to set up a protocol for communication,i.e. packet length, etc. If bind stack service is requested, an IPXMUXBind Stack API handler in step 1394 is called, which forces IPXODI tobind to the wired LAN card 1352 to which IPXODI is bound before thewireless LAN card 1360 was installed in order to be compatible with theIPXODI protocol. The IPXMUX bind stack handler also saves the process IDof the binding for sending and receiving packets.

If the protocol API call is not a register protocol stack or a bindstack service, the system checks in step 1396 whether send packetservice is requested. If not, the system exits and the service call ishandled by LSL.COM. If so, an IPXMUX send packet routine is called instep 1398 and 1400 (FIG. 51), which sets the address of the wireless LANcard 1360 as the source node address in step 1402. The packet modifieralso sets the node address of the wireless interface device 100 as thepacket's destination mode address in step 1400 (FIG. 51). The send eventservice routine address is set to the address of the send event serviceroutine in IPXMUX.COM before it returns.

Incoming packets are handled by an incoming packet handler illustratedin FIG. 32. In particular, incoming packets are checked in step 1404whether the source address of the packet is from the wireless LAN card1360. If not, the system returns. If so, the packet's source modeaddress is saved and set to the mode address of the wireless LAN card1360 while the pocket destination address is set to the address of thewired LAN card 1352 to which IPOXDI is bound.

14. Host Control Mode

The wireless interface device 100 includes a hot icon 1408 (FIG. 37) inthe hot icon area 1202 (FIG. 36) of the LCD 113C for switching controlof the host computer 101 from the wireless interface device 100 and thehost computer 101. While the wireless interface device 100 has controlof the host computer 101, the user has the option to dim the screen ofthe host computer 101, as well as lock out the keyboard and mouseinputs. In particular, with reference to FIG. 37, a set-up window hoticon 1410 may be selected. Activation of the set-up window icon causesone of five selectable set-up dialog boxes to be displayed in theviewing area 1200 (FIG. 36) of the LCD 113C on the wireless interfacedevice 100. These dialog boxes are illustrated in FIGS. 53-57, which canbe selected by a graphical button bar 1412 (FIG. 53). When the "host"button is selected, a list of host computer groups that are accessibleby the wireless interface device 100 as well as the specific host towhich the wireless interface device 100 is connected are displayed. Whenthe wireless interface device 100 has control of the host computer 101,the host computer screen can be dimmed and the host keyboard and mousecan be locked out by placing the pen down in the box next to thosefunctions in the dialog box illustrated in FIG. 53. FIG. 54 relates tosetting up remote keyboard macros. FIG. 55 is a maintenance dialog boxwhich enables various maintenance functions, such as calibration of thepen, rebooting of the host, and the like. FIG. 56 relates to powersettings, and in particular includes an inactivity timer for timingperiods of inactivity in order to place the wireless interface device100 in a low-power state. FIG. 57 is selectable by the screen button andenables the brightness and contrast of the LCD 113C on the wirelessinterface device 100 to be adjusted.

FIG. 58 illustrates a method for disconnecting the host computer 101from the wireless interface device 100 and automatically returningcontrol of host screen, keyboard and mouse to the host computer 101. Inaddition, any configuration settings of the wireless interface device,such as contrast and brightness adjustment, are also saved in order toobviate the need to readjust the wireless interface device 100, the nexttime it is connected.

Initially in step 1414 (FIG. 58) the system determines if the hot iconarea 1202 of the LCD 113C on the wireless interface device 100 waspressed. As illustrated in FIG. 37, the hot icon area 1202 includesseveral hot icons. Thus, the system checks in step 1416 whether the hostcontrol mode hot icon 1408 (FIG. 37) was selected. If not, the systemloops back to step 1414 and waits for the hot icon area to be pressed.If the host control mode hot icon 1408 was selected, the wirelessinterface device 100 sends a private message (i.e. pocket) to the hostcomputer 101 in step 1418, requesting host control mode.

The system then checks in step 1420 whether the host computer 101returned an acknowledgement that the private message was received. If anacknowledgement of the private message is not received by the wirelessinterface device 100, the attempt to enter the host control mode isaborted in step 1422. If an acknowledgement is received, the systemchecks in step 1424 if the mouse keyboard and mouse had been previouslylocked out by the wireless interface device 100 as discussed above. Ifso, the host keyboard and mouse are unlocked. Subsequently in step 1426,an internal flag is set indicating a request for termination of theconnection with the host computer 101 in step 1428. The request fortermination initiates a timer, which, when timed out, disconnects thewireless interface device 100 from the host computer 101. Thus, thesystem checks to determine if the host computer 101 is still connectedto the wireless interface device 100 in step 1430. If so, the systemdetermines if the request for termination has timed out in step 1432. Ifnot, the system waits for the timer to time out and disconnects thewireless interface device 100 from the host computer 100. Once thewireless interface device 100 is disconnected, control of the hostcomputer 101 is returned to the host computer 101.

In order to obviate the need to reconfigure the wireless interfacedevice 100 the next time the wireless interface device 100 is connectedto the host computer 101, the system checks in step 1434 whether any ofthe configuration data (i.e. contrast, brightness (FIG. 57) was changed.If not, the wireless interface device 100 is placed in a suspend mode instep 1436. If the configuration data did change, the new configurationdata is saved in the EEPROM 111B (FIG. 12) in step 1438.

15. Broadcast for Available Hosts

The wireless interface device 100 can determine the available hostswithin range for wireless connection. The user can then select a host byway of a dialog box (FIG. 53), which will be discussed in more detailbelow. An important aspect of the wireless interface device 100 is thatit can be connected to virtually any available hosts without anyphysical connections and without knowing the host address or nodeaddress beforehand, unlike known wireless and wired LAN systems wherethe node addresses of each of the personal computers in the network havea preassigned node address and are therefore known prior to anycommunications being established.

In order to initiate connection of the wireless interface device 100 toan available host 101, the set-up hot icon 1410 (FIG. 37) is selected instep 1439 (FIG. 59) which causes a set-up dialog box, as illustrated inFIG. 53 to be displayed in the viewing area 1202 (FIG. 36) of the LCD113C. Subsequently, in step 1440, the wireless interface device 100broadcasts network packets to be received by all available hosts 101 inrange that are on the same channel and domain as the wireless interfacedevice 100. After the network packets are broadcast, the wirelessinterface device 100 listens for a predetermined time period in steps1442 and 1444 for return acknowledgement packets from the availablehosts 101, which contain, among other things, the node addresses of theavailable hosts 101. After the time-out period the wireless interfacedevice 100 terminates listening for responses from the available hosts101 in step 1446. After listening is terminated, the system checks thenumber of responses received in step 1448. If no responses are received,the wireless interface device 100 repeats the cycle (i.e. returns tostep 1440) for a predetermined number of retries as determined in step1450.

If a response is received, the system identifies the unique node addressfrom the responding hosts 101 in step 1452 and saves the unique hostnode addresses in step 1454. The list of available hosts 101 is searchedin step 1456 for duplicate serial numbers. Should duplicate serialnumbers be found in step 1458, a warning is generated in step 1460,warning the user that a duplicate copy of software is running on one ofthe responding hosts 101. In step 1462, the currently connected host isforced to appear as unavailable on the dialog box illustrated in FIG.53.

The responding hosts 101 are sorted first by group name and then by hostname in step 1464. After the sorting, an internal status list of theavailable hosts 101 in designated as available in step 1466.Subsequently, the available hosts and groups are displayed in the dialogbox illustrated in FIG. 53 in step 1468. Movement of the cursor (by apen-down event) to the desired host 101 selects that host 101. A"connect" button on the dialog box is then selected to connect thewireless interface device 100 to the selected host 101.

16. Remote Keyboard Macros

FIGS. 60 and 61 relate to remote keyboard macros on the wirelessinterface device 100. An important aspect of the wireless interfacedevice 100 is that the remote keyboard macros are provided by way of awireless connection. FIG. 60 relates to developing the macros while FIG.61 is directed to using the macro.

Referring to FIG. 37, the wireless interface device 100 includes twouser-defined hot icons 1472 and 1474, located in the hot icon area 1202(FIG. 36) of the LCD 113C, that can be used for the macros. These hoticons 1472 and 1474 are configurable in a set-up mode, which, asdiscussed above, is under the control of the set-up hot icon 1410 (FIG.37). Once the set-up hot icon 1410 is selected, a hot key button 1470 onthe dialog box illustrated in FIG. 54 is selected. As noted in FIG. 54,the dialog box includes two configurable macros. These macros areconfigured by way of the two edit fields 1472 and 1474 (FIG. 54). Inorder to configure the macros, the icon for the desired edit field 1472or 1474 is selected. These edit fields 1472 and 1474 are configurable byway of a virtual on-screen keyboard (OSK), selectable by way of a hoticon 1480 (FIG. 37).

Referring to FIG. 60, the system checks in step 1476 whether there hasbeen a pen-down event in the viewing area 1202 (FIG. 36) of the LCD 113Cand, in step 1478, whether the OSK hot icon 1480 (FIG. 37) was selected.If not, the system loops back to step 1476. If so, the selected key onthe OSK is translated into a keyboard scan code in step 1480 and avisual indication of the key selected in the edit field 1472 or 1474 instep 1482. The process is repeated until the macro (i.e. WIN, DIR),followed by a carriage return 1486, is complete and the macro is savedin the EEPROM 111B (FIG. 12) in step 1484. A clear button 1486 isprovided in the dialog box illustrated in FIG. 54 for each edit field1472 and 1474. These clear buttons 1486 enable the edit fields to becleared in the EEPROM 111B (FIG. 12).

Activation of the remote keyboard macros is accomplished by pressingdown on the user-defined hot icons 1472 or 1474, located in the hot iconarea 1202 (FIG. 36) of the LCD 113C. The system checks in steps 1486 and1488, whether the user defined hot icons 1472 or 1474 are selected. Ifthe user-defined hot icons 1472 or 1474 are not selected, the systemreturns to step 1486. Once one of the user-defined hot icons 1472 or1474 is selected, the keyboard scan code sequence, stored in the EEPROM111B (FIG. 12), is retrieved for the selected hot icon 1472 or 1474 instep 1490, which are then individually transmitted to the host 101 instep 1492. These scan codes are then written to the keyboard buffer onthe host 101 in step 1494. Subsequently, in step 1496, the host 101processes the scan codes as though they originated from the hostkeyboard.

17. Wireless Flash Programmer

As mentioned above, the wireless interface device 100 includes severalflash memory devices 742-748 (FIG. 25). The flash memory device 742includes a protected area which contains the system BIOS, and asufficient amount of functionality to enable the wireless interfacedevice 100 to be rebooted to enable reprogramming of the flash memorydevices 742-748 by way of the serial port 788 (FIG. 23) in the event ofa flash disaster.

In order to upgrade the flash memory devices 742-748, the upgrade disksare installed in an available host computer 101. In particular, theflash upgrade software is written to a predetermined directory on thehost's 101 hard disk. After the flash upgrade disks are installed, thewireless interface device 100 is turned on in step 1498 (FIG. 62A) byway of the main power switch 855 (FIG. 28). Subsequently, in step 1500,a connection between the host computer 101 and wireless interface device100 is initiated in step 1500 by first selecting the configuration hoticon 1410 (FIG. 37).

Subsequently, the maintenance button on the dialog box is selected toget to the dialog box illustrated in FIG. 55. An upgrade button 1502 onthe dialog box illustrated in FIG. 55 is selected in step 1504. In orderto prevent programming errors, the radio quality is checked in step 1506before proceeding. If the radio quality is poor, the upgrade is aborted.If the radio quality is adequate, power management is disabled in step1508 to prevent the wireless interface device 100 from going into areduced power state as discussed above during programming of the flashmemory devices 742-748. After the power management is disabled, aportion of the DRAM memory 111A (FIGS. 18 and 24) in the wirelessinterface device 100 is set aside to receive a flash sector from thehost computer 101 in step 1510. Subsequently, the wireless interfacedevice 100 polls the host computer 101 to determine the correct numbersof sectors in the flash update and whether the sectors are available onthe hard disk of the host computer 101 in steps 1512 and 1514. If theflash update files are not on the host hard drive or an incorrect numberof sectors are available on the host hard disk, the update is aborted.Otherwise, the system requests the path/file data from the host computer101 in step 1516. Subsequently, each sector (file) in the flash updateis read by the host computer 101 and uploaded over the radio to the DRAM111A in the wireless interface device 100 in step 1518. After thesectors are written to the DRAM 111A in the wireless interface device100, a BIOS call is made to write the sectors in the DRAM 111A to theflash memory devices 742-748 in step 1520.

In step 1522 the system checks for errors in writing to the flash memorydevices 742-748. Should any errors be detected, the update is aborted.If no errors are detected, the system checks in step 1524 whether all ofthe sectors from the DRAM 111A have been written to the flash memorydevices 742-748 in the wireless interface device 100. If not, the systemloops back to step 1516. Once all of the files have been transferred tothe flash memory devices 742-748, the wireless interface device 100 isrebooted in step 1526. Once the wireless interface device is rebooted,the system will be able to utilize the updated software in the flashmemory devices 742-748.

FIGS. 63A and 63B illustrate the routine for writing the flash updatesectors from the DRAM 111A to the flash memory devices 742-748. Sincethe flash updates are stored in the DRAM memory 111A, the programming isaborted if the AC power is turned off as determined in step 1528 sincethe flash update data in the DRAM 111A will be lost when the battery isexhausted. In order to prevent errors during programming, interrupts, aswell as the power management, are disabled on the wireless interfacedevice 100 in steps 1530 and 1532. After the interrupts and the powermanagement are disabled, the flash memory device is erased in step 1534.If errors occur during erasure, as determined in step 1536, updating ofthe particular flash memory device 742-748 is aborted. If not, a sectorfrom the DRAM 111A is written to the flash memory devices 742-748 instep 1538. After the sector is written to the flash memory devices742-748, the system checks in step 1540 whether any errors occurred. Ifso, the update is aborted. If not, the interrupts, as well as the powermanagement, are enabled in step 1542 when all sectors have beenreflashed.

18. Automatic Reconnect

As mentioned above, the wireless interface device 100 can be connectedto any of the available hosts 101 that appear in the dialog boxillustrated in FIG. 53 in the manner described above. The systemillustrated in FIGS. 64A and 64B obviates the need for the user toselect a host 101 for connection each time the wireless interface device100 is powered up, by automatically connecting the wireless interfacedevice 100 to the last host 101 to which it was successfully connected.As will be discussed in more detail below, when a host 101 is selectedfrom the dialog box illustrated in FIG. 53 for connection to thewireless interface device 100 and a connection is successfully achieved,the node address of that host 101 is stored in the EEPROM 111B (FIG.12). Subsequently, once the wireless interface device 100 is powered upin step 1544, the system 1o reads the node address from the EEPROM 111B,and reads it to a specific location in DRAM 111A (FIGS. 18 and 24) instep 1546. After the node address is written to the DRAM 111A, thesystem checks the node address to determine whether it is valid in step1548. Invalid node addresses 15occur anytime the wireless interfacedevice 100 makes an attempt to connect to a host 101, which fails duringautomatic reconnecting or is later disconnected by the end user. Thus,if a successful connection is not made or if there is a manualdisconnection, the node address is cleared from the DRAM 111A in step1550 and thus will be invalid. Subsequently, if the automatic reconnectfails in order to facilitate connection of the wireless interface device100 to another available host 101, the set-up dialog box illustrated inFIG. 53 is displayed on the display 113C of the wireless interfacedevice 100 in step 1552. After the host selection set-up dialog box isdisplayed on the wireless interface device 100, the system checks instep 1554 whether the wireless interface device 100 is connected to anavailable host 101. Normally, if an invalid address is found in step1548 and the host selection set-up dialog box appears on the display113C of the wireless interface device 100, there will be no connectionto an available host 101 and the system will jump to step 1556, where itchecks if the hot icon area 1202 (FIG. 37) has been depressed. Normallyin this situation, since the host selection dialog box is already beingdisplayed on the screen 113C of the wireless interface device 100, theonly hot icon that can affect the situation is a sleep-face hot icon1558 (FIG. 37), which places the wireless interface device 100 in alow-power sleep mode. In a normal situation when the wireless interfacedevice 100 is first powered up, the sleep-faced hot icon 1558 is notdepressed and the system waits for the user to select an available host101 from the host set-up dialog box illustrated in FIG. 53 as discussedabove in step 1560. Once an available host 101 is selected, the systemloops back to step 1562 and attempts to establish connection with theselected host 101.

In step 1564 the system checks whether or not the connection wassuccessful. If not, the system goes to step 1550 and clears the nodeaddress for the selected host 101 from the DRAM 111A and displays thehost selection set-up dialog box in step 1552. If the connection betweenthe wireless interface device 100 and the host 101 is successful, thenode address of the host 101 is saved in a specific DRAM location instep 1566, and in turn, written to the EEPROM 111B (FIG. 12) in step1568. After the node address of the selected host 101 is stored inEEPROM 111B, the wireless interface device 100 will display whatever isbeing displayed on the host 101 in step 1570.

After a connection is established between the host 101 and the wirelessinterface device 100, the system continuously checks for hot icons beingselected in step 1572. If no hot icons are selected, the system willloop back and continue to check for the selection of a hot icon. If thesystem determines that a hot icon is selected, the system checks in step1574 whether the set-up dialog hot icon 1410 (FIG. 37) was selected. Ifso, the system loops back to step 1552 and displays the host selectionset-up dialog box illustrated in FIG. 53 on the display 113C of thewireless interface device 100. If the set-up dialog hot icon 1410 is notselected, the system checks in step 1576 whether the sleep-face hot icon1558 is selected in step 1576. If not, the system checks in step 1578whether other hot icons in the hot icon area 1202 (FIG. 36) wereselected and the appropriate action is taken. The system then goes tostep 1570 and, in turn, and continually checks for the selection ofother hot icons in step 1572.

If it is determined in step 1576 that the sleep-face hot icon 1410 isselected, the system checks in step 1580 whether a double pen-down eventoccurred at the location of the sleep-face hot icon 1410. As mentionedabove, the sleep-face hot icon 1410 causes the wireless interface device100 to go into a low-power mode. However, before placing the wirelessinterface device 100 in a low-power mode, the node address of the host101 to which the wireless interface device 100 is connected is saved ina specific location of the DRAM 111A and, in turn, written to the EEPROM111B in step 1582. After the node address is saved, the wirelessinterface device 100 is powered down in step 1584.

The system discussed above is thus able to automatically connect thewireless interface device 100 to the last host 101 to which it wasconnected. After the automatic reconnect, should the set-up window hoticon 1410 (FIG. 37) be selected, the host selection set-up dialog boxillustrated in FIG. 53 will be displayed on the screen 113C of thewireless interface device 100. Subsequently, the system will go to step1554 and check whether the wireless interface device 100 is connected toa host 101. In this case, since the wireless interface device 100 willstill be connected to the available host, the system then checks in step1586 whether a disconnect button on the host selection dialog boxillustrated in FIG. 53 has been depressed. If not, the system goes tostep 1556 and continuously waits for a hot icon in the hot icon area1202 (FIG. 36) of the LCD 113C to be depressed. If the disconnect buttonin the host selection set-up dialog box illustrated in FIG. 53 isdepressed, the node address for the host 101 to which the wirelessinterface device 100 is connected is erased from the specific locationin the DRAM 111B in step 1588. Subsequently, the system goes to step1556 and waits for a hot icon in the hot icon area 1202 (FIG. 37) to bedepressed.

19. Remote Occlusion Region

As mentioned above, the wireless interface device 100 includes a virtualon-screen keyboard (OSK), as illustrated in FIG. 66. More particularly,the OSK is configurable by the buttons 1590, 1592, 1594 and 1596 in acontrol box located at the top of the OSK. These buttons 1590, 1592,1594 and 1596 enable the OSK to be configured. For example, a button1590 displays the OSK as illustrated in FIG. 66A with a full keyboardand numeric keypad. The button 1592 is a toggle which displays thekeyboard without the numeric keyboard as illustrated in FIG. 66B. Thebutton 1594 displays the numeric keypad with the NUM LOCK off asillustrated in FIG. 66C, or alternatively displays the OSK as a numerickeyboard NUM LOCK on as illustrated in FIG. 66D. The button 1596 allowsthe size of the OSK to be varied. The "X" button closes the windowdisplaying the OSK.

As mentioned above, the display 113C on the wireless interface device100 displays whatever is being displayed on the host 101 when aconnection is made. Since the graphics for the OSK is generated locallyat the wireless interface device 100, a remote occlusion region isgenerated at the host 101 to prevent the host 101 from painting over theOSK on the display 113C of the wireless interface device 100. The remoteocclusion region is analogous to a window in the display of the host 101in which the host 101 is prevented from using.

Referring to FIG. 65A, the system monitors the hot icon area 1202 (FIG.36) to determine if any of the hot icons have been pressed. As discussedabove, the system includes an OSK hot icon 1480 (FIG. 37), whichdisplays the OSK on the LCD 113C of the wireless interface device 100when depressed. If the system determines in step 1598 that a hot iconhas been depressed, it checks in step 1600 whether the OSK hot icon 1480was pressed. If not, the system loops back to 1598 and continuallychecks for hot icons being pressed. If the OSK hot icon 1480 has beendepressed, the system determines the last configuration for the OSK instep 1602 (i.e. FIGS. 66A-66D). Once the configuration of the last OSKis determined in step 1602, the system then checks the operating systemand video mode of the host 101 in step 1604. Depending on whether thehost 101 is in text or graphics mode will determine whether the OSKimage on the wireless interface device 100 is merely shadowed onto thedisplay of the host 101 by way of a private message, as will bediscussed in more detail below, or whether the remote occlusion regionat the host 101 is established by drivers in the host software, whichcreate the remote occlusion region by way of ASCII characters. Thus, instep 1606, if the system determines that the host 101 is in the textmode, an occlusion region on the display of the host 101 is createdusing the host control drivers in step 1608. In step 1610, the systemchecks whether the occlusion region was successfully established. Ifnot, the system then checks in step 1612 whether the OSK is currentlyvisible on the display 113C of the wireless interface device 100. Ifnot, the display of the OSK is aborted in step 1614. If it is determinedin step 1612 that the OSK is currently visible on the LCD 113C of thewireless interface device 100, any reconfiguration of the OSK is ignoredand the configuration of the last OSK is continuously displayed in step1614. If it is determined in step 1610 that the remote occlusion regionis successfully established, the system goes to step 1616, which enablesthe OSK to be used.

If it is determined in step 1606 that the host 101 is not in a textmode, the system checks in step 1618 whether the host 101 is in agraphics mode. If not, the system goes to step 1620 and sets the videomode to VGA graphics in the wireless interface device 100 andsubsequently proceeds to step 1608 to establish the occlusion region inthe host 101 by host control drivers. If the host is in a graphics mode,the system next checks in step 1622 whether the host 101 is running aWindows application. If not, the system returns to step 1608 andestablishes the occlusion region on the display of the host 101 usingthe host control drivers.

If it is determined in step 1622 that the host 101 is running a Windowsapplication, the occlusion region on the host 101 is established by wayof a private message sent by the wireless interface device 100 to thehost 101 in step 1624. After the private message is sent, the systemchecks in step 1626 to determine if it was successfully sent. If not,the system proceeds to step 1612 and checks to determine if an OSK iscurrently visible. If the private message is successfully sent, thesystem checks in step 1628 whether the private message was successfullyreceived by the host 101. If so, the system goes to step 1630 and checkswhether the private message was acknowledged by the host 101. If so, thesystem goes to step 1616 and draws the OSK at the user-requestedcoordinates. If not, the system goes to 1612. If it is determined instep 1628 that the private message has not been received, the systemcontinually checks for receipt of the private message for apredetermined time-out period in step 1632. Should a time-out occurbefore the private message is acknowledged by the host 101, the systemagain will go to step 1612.

The OSK includes a control bar 1632 (FIG. 66A). The control bar 1632enables the location of the OSK on the LCD 113C of the wirelessinterface device 100 to be changed by touching the control bar 1632 withthe pen and dragging it to the desired location on the LCD 113C of thewireless interface device 100. Anytime the user changes the location ofthe OSK on the LCD 113C of the wireless interface device 100 asacknowledged by the system in step 1634, the system then returns to step1604 to determine the video mode of the host computer 101. As discussedabove, the video mode determines whether the remote occlusion region onthe display of the host 100 is created by shadowing the OSK on thedisplay of the host by way of the private message or whether theocclusion region on the display of the host is created by local driversusing ASCII characters. The system then goes to step 1606.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. Thus, it is to beunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described above.

What is claimed and desired to be secured by Letters Patent of theUnited States is:
 1. A wireless interface device for use with one ormore host computers, the wireless interface device comprising:means forcommunicating with one of said one or more host computers; means forenabling said wireless interface device to take control of one of saidone or more host computers after communication is established; means forstoring a node address corresponding to the last host computer to whichthe wireless interface was successfully connected; means fordetermining, on power up, the availability of a connection to the lasthost computer; means for updating said node address to indicate analternative host computer upon determining that said connection is notavailable; and means for automatically connecting said wirelessinterface device to the host indicated by said node address.
 2. Awireless interface device according to claim 1, said connecting meansincluding means for checking a validity of said node address.
 3. Awireless interface device according to claim 1, further including meansfor enabling said wireless interface device to enter a power down state.4. A method for operating a wireless interface device in a system withone or more host computers:communicating with one of said one or morehost computers; enabling said wireless interface device to take controlof one of said one or more host computers after communication isestablished; storing a node address corresponding to the last hostcomputer to which the wireless interface was successfully connected;means for determining, on power up, the availability of a connection tothe last host computer; updating said node address to indicate analternative host computer upon determining that said connection is notavailable; and automatically connecting said wireless interface deviceto the host indicated by said node address.
 5. A method according toclaim 4, further including:checking a validity of said node address. 6.A method according to claim 4, further including entering a power downstate.
 7. A wireless interface device for use with one or more hostcomputers, the wireless interface device comprising:means forcommunicating with one of said one or more host computers; means forenabling said wireless interface device to take control of one of saidone or more host computers after communication is established; means forautomatically connecting said wireless interface device to the last hostto which it was successfully connected on power-up, said connectingmeans including means for identifying a node address of said last host,means for storing said node address, and means for checking a validityof said node address; and means permitting said wireless interfacedevice to enter a power down state, wherein said storing means isconfigured to store said address prior to said wireless interface deviceentering said power down state.
 8. A method for operating a wirelessinterface device in a system with one or more hostcomputers:communicating with one of said one or more host computers;enabling said wireless interface device to take control of one of saidone or more host computers after communication is established;automatically connecting said wireless interface device to the last hostto which it was successfully connected on power-up; identifying a nodeaddress of said last host; checking a validity of said node address;storing said address prior to said wireless interface device entering apower down state; and entering said power down state.
 9. A wirelessinterface device for use with one or more host computers, the wirelessinterface device comprising:a radio transceiver for communicating withone of said one or more host computers; a memory storing a node addresscorresponding to the last host computer to which the wireless interfacewas successfully connected; a processor determining, on power up, theavailability of a connection to the last host computer, and upondetermining that said connection is not available, updating said nodeaddress to indicate an alternative host computer, said processorautomatically connecting said wireless interface device to the hostindicated by said node address.